Aback When a sail is aback, the wind fills it from the wrong side, pressing it against the mast. This usually happens by mistake and slows or stops the vessel’s forward motion.

Abaft Toward the rear (stern) of the vessel, relative to a specific point. For example, “abaft the mast” means behind the mast.

Abaft the Beam Located or moving behind an imaginary line drawn at a right angle to the ship’s centerline—closer to the stern than the midpoint.

Abandon Ship An emergency order to leave the vessel immediately when staying aboard is unsafe or life-threatening.

Abeam Positioned directly at right angles to the ship’s keel—off the side of the vessel.

Aboard On or within a ship. The phrase “close aboard” means near the side of the vessel.

Above Board An expression meaning honest, open, and visible—originally used for actions done on deck rather than hidden below.

Accommodation Living quarters provided for passengers or crew on a ship.

Accommodation Ladder A portable staircase or gangway fixed to a ship’s side, used for boarding or leaving the vessel safely.

Admiral A high-ranking naval officer, typically in command of a fleet or major naval formation.

Admiralty The governing authority or department in charge of a nation’s naval affairs.

Admiralty Chart An official nautical chart published by the Admiralty, showing coastal features, depths, and navigation information.

Admiralty Law The body of law governing maritime activities, including navigation, shipping, and marine commerce.

Adrift Floating freely without control, anchor, or steering; not secured or under command.

Aft Toward or at the stern (rear) of the ship.

After Bow Spring Line A mooring line running forward from the stern of a vessel to prevent backward movement when docked.

Aftcastle A raised structure at the stern of older sailing ships, used for command or living quarters.

Aground When a ship’s bottom touches the seabed or shore, preventing it from floating freely.

Ahead In the forward direction; in front of the vessel’s bow.

Ahoy A traditional call used to hail another vessel or attract attention at sea.

A-hull A storm tactic in which a vessel rides out severe weather with sails down and the helm secured to leeward.

Aid to Navigation (ATON) Any fixed or floating device—such as buoys, beacons, or lights—used to help mariners determine position, direction, or warn of hazards.

Airdraft The vertical distance from the waterline to the highest point on a vessel, important for clearing bridges or overhead obstacles.

AIS (Automatic Identification System) An electronic tracking system that transmits and receives vessel information such as name, speed, and position to improve maritime safety.

Albatross A large oceanic bird often seen by sailors; once believed to bring good luck at sea.

All Hands A phrase referring to the entire crew of a ship.

Allision The act of one moving vessel striking a stationary object or another ship.

Alongside By the side of another vessel or a dock, close enough for transfer or mooring.

Aloft Above the deck, usually referring to the rigging, masts, or higher parts of the ship.

Amidships The central portion of a vessel, midway between the bow and stern.

Anemometer An instrument used to measure wind speed and sometimes direction.

Anchor A heavy device lowered to the seabed to hold a vessel in place.

Anchor Ball A black spherical signal hoisted in the forepart of a vessel during daylight to indicate it is anchored.

Anchor Buoy A small floating marker attached to the anchor to show its location on the seabed.

Anchor Chain or Cable The chain or rope that connects a vessel to its anchor.

Anchor Detail The designated crew team responsible for operating and securing the anchor equipment.

Anchor Light A white light displayed at night by an anchored vessel to show its position.

Anchor Rode The combined length of line, chain, or cable that links the anchor to the boat.

Anchor Watch A lookout or duty period when crew members monitor the ship at anchor to ensure it is not drifting.

Anchorage A designated area or suitable location where ships can safely anchor.

Anchor’s Aweigh The moment when the anchor is lifted clear of the seabed and the ship is free to move.

Apparent Wind The wind felt aboard a moving vessel—a mix of the true wind and the wind created by the ship’s motion.

Apron The deck area immediately in front of a cabin entrance or companionway.

ARPA (Automatic Radar Plotting Aid) A radar system that automatically tracks nearby vessels and calculates their course to help avoid collisions.

Armament The weapons and defensive equipment carried by a naval vessel.

Ashore On or moving toward the shore.

Asylum Harbor A safe harbor where vessels can seek shelter during bad weather or emergencies.

Astern Behind or toward the rear of a vessel; also used when a ship moves backward.

Athwart / Athwartships Across the ship from one side to the other, at right angles to the centerline.

Auxiliary Engine A secondary engine used for generating power or as emergency propulsion.

Auxiliary Vessel A ship designed to support other vessels, typically providing supplies, maintenance, or operational assistance.

Avast A command meaning stop or cease immediately.

Awash So low in the water that waves or spray continually wash over the surface.

Aweigh When an anchor is raised just clear of the sea bottom.

Aye, Aye A sailor’s response meaning “I understand and will carry out your order.”

Azimuth The compass bearing of a celestial or terrestrial object, measured clockwise from true north.

Azimuth Circle A device attached to a compass for taking accurate bearings of objects or celestial bodies.

Azimuth Compass A compass equipped with an azimuth circle, allowing precise measurement of directions and bearings.

Back and Fill A sailing technique that uses the tide’s current to help maneuver when the wind is unfavorable, often applied in narrow channels or while docking.

Backstays Strong cables or ropes running from the top of the mast toward the stern, used to support and stabilize the mast.

Baggywrinkle A soft, fuzzy covering made from old rope, wrapped around rigging to protect sails from chafing.

Ballast Weight placed in the lower part of a boat to increase stability and balance, preventing it from capsizing.

Ballast Tank A watertight compartment used to hold water or other ballast material, adjusting the vessel’s stability and trim.

Bar A ridge of sand, gravel, or sediment formed by tidal currents at river mouths or harbor entrances, often affecting navigation.

Bar Pilot A skilled navigator who guides vessels through shallow or difficult channels near harbor bars or river mouths.

Barque A sailing ship with three or more masts, square-rigged on all except the aftmost mast, which carries fore-and-aft sails.

Barometer An instrument used to measure atmospheric pressure and predict weather changes.

Barrelman A lookout stationed in the crow’s nest, responsible for spotting other ships, land, or hazards at sea.

Batten A narrow strip of wood or plastic inserted into pockets on a sail to maintain its shape and reduce fluttering.

Batten Down To secure hatches, sails, and loose gear in preparation for rough weather.

Beam The widest part of a boat’s hull, critical for determining stability and interior space.

Bear Away (or Bear Down) To steer a vessel away from the direction of the wind.

Bearing The direction of an object or point, measured in degrees relative to a vessel’s current position or compass heading.

Becalm To lose wind in the sails, causing a sailing vessel to stop moving.

Before the Mast A phrase describing the living area for enlisted sailors, located toward the forward part of older ships.

Belaying Pins Short, sturdy rods fixed in a rack on deck, used for securing ropes and rigging lines.

Bell Buoy A floating navigational aid fitted with a bell that rings as it moves with the waves, warning mariners of hazards.

Berth A sleeping space for a crew member on a vessel, or a designated mooring spot for a ship in a harbor.

Best Bower The primary and largest anchor carried by a ship, used for secure anchoring in normal conditions.

Bilge The lowest interior part of a ship’s hull where water and waste tend to collect.

Bilge Keel A fin-like projection along the lower sides of a ship’s hull that helps reduce rolling motion.

Bilge Pump A mechanical or manual pump used to remove water that gathers in the bilge.

Bimini A canopy made from fabric and supported by a metal frame, providing shade and weather protection for the cockpit area.

Binnacle A stand or housing near the ship’s helm that holds the magnetic compass and sometimes other navigation instruments.

Bitter End The final section of a rope or anchor chain; the part secured to the ship.

Bitts Strong vertical posts on deck used for securing lines or cables, especially during mooring.

Block A pulley used to redirect or increase the mechanical force of a line or rope.

Boat Hook A long pole with a hook on the end, used for pushing, pulling, or retrieving objects from the water.

Boatswain (Bosun) A senior crew member responsible for the ship’s equipment, maintenance, and deck operations.

Boom A horizontal spar attached to the mast’s lower section, controlling the foot of a sail.

Boom Vang A tackle system that controls the angle and tension of the boom, improving sail shape and performance.

Bow The front or forward part of a ship or boat.

Bow-Chaser A long-range gun mounted at the front of a ship, used historically to fire directly ahead during pursuit.

Bowline A strong knot forming a fixed loop at the end of a rope, widely used for securing or towing.

Bow Thruster A propulsion device located at the bow that allows a vessel to move sideways, aiding in docking and maneuvering.

Bowsprit A spar extending forward from a ship’s bow, supporting the fore-sails and providing extra sail area.

Breakwater A barrier built offshore or along a coastline to protect a harbor or beach from waves and erosion.

Bridge The command center of a ship where navigation and steering are controlled.

Brig A two-masted sailing vessel with square sails on both masts; also, the term for a ship’s jail.

Broaching-To A dangerous situation where a vessel turns unexpectedly broadside to heavy waves or wind, risking capsizing.

Bulk Carrier A ship designed to transport large quantities of unpackaged cargo such as coal, ore, or grain.

Bulkhead A wall or partition inside a ship that divides compartments, adding structural strength and safety.

Bulwark The solid extension of a ship’s sides above the deck, providing protection for crew and equipment.

Bunkering The process of supplying fuel to a ship.

Burgee A small, triangular flag that identifies a yacht club or serves as a wind direction indicator.

Buoy A floating marker used to indicate channels, hazards, or anchorage points.

Buoyancy The upward force exerted by water that allows objects to float.

By the Lee Sailing with the wind coming from behind and on the same side as the boom, a position that increases the risk of an accidental jibe.

Cabin An enclosed space on a ship used for living, sleeping, or working.

Cable A heavy rope or chain used for anchoring or towing.

Cable Length A nautical measurement equal to one-tenth of a nautical mile, or roughly 600 feet (about 185 meters).

Camber The slight upward curve of a ship’s deck, designed to help water drain off quickly.

Can Buoy A cylindrical-shaped buoy marking the left side of a channel when entering from seaward.

Capstan A vertical, rotating drum used for winding ropes or cables, often to raise the anchor or other heavy loads.

Capsize When a vessel overturns or rolls completely onto its side or upside down.

Captain The commanding officer of a ship, responsible for navigation, safety, and overall operation.

Carvel Build A traditional method of wooden ship construction in which hull planks are fitted edge to edge, creating a smooth exterior surface.

Cast Off To release a vessel from its moorings or lines so it can depart.

Catamaran A vessel with two parallel hulls connected by a deck or frame, known for speed and stability.

Catch a Crab A rowing term describing when an oar blade gets stuck in the water due to poor timing or technique.

Cathead A strong timber or metal beam projecting from the bow, used for raising and securing the anchor.

Caulk To seal the seams between planks on a wooden hull to make it watertight.

Celestial Navigation The practice of determining a ship’s position using the sun, moon, stars, and planets.

Centerboard A retractable keel that can be lowered to improve stability and reduce sideways drift.

Chart A nautical map showing coastlines, depths, hazards, and navigation aids.

Chart Datum The reference level from which charted depths and tidal heights are measured.

Chart Room A compartment or area on a ship where charts, instruments, and navigational tools are stored and used.

Chine The sharp angle where the bottom and sides of a flat- or V-bottomed boat meet.

Chock A metal or wooden fitting through which ropes or hawsers are led to prevent chafing.

Chronometer A highly accurate clock used at sea to determine longitude by comparing local time with Greenwich Mean Time.

Cleat A device with projecting arms around which ropes can be fastened.

Clew The lower corner of a sail where the sheets are attached.

Clinker Build A method of wooden boat construction where each plank overlaps the one below it, creating a ridged surface.

Close-Hauled Sailing as directly into the wind as possible while keeping the sails filled.

Coaming A raised border around hatches or cockpit openings that prevents water from entering.

Coastal Waters The areas of the sea near land, generally within 12 nautical miles of the coast.

Cockpit The open area where the helm and sailing controls are located, often where the crew operates the boat.

Companionway A staircase or ladder leading from one deck level to another, often from the deck to the cabin.

Compass A navigation instrument showing direction relative to the Earth’s magnetic poles.

Compass Rose A circular diagram on nautical charts that shows cardinal directions and degrees for navigation.

Compressor A machine used to compress air, commonly for diving tanks or shipboard tools.

Con To direct or steer a ship’s course under the captain’s orders.

Conning Tower A protected, elevated area on a naval ship or submarine from which it is navigated or commanded.

Course The intended direction or path a vessel follows across the water.

Coxswain The crew member in charge of steering and commanding a small boat.

Crab A mechanical device used to grip or lift a cable, or a rowing mishap where an oar catches the water incorrectly.

Cradle A wooden or metal frame that supports a vessel during building, repair, or storage on land.

Craft A general term for any type of vessel that travels on water.

Crane A mechanical device used for loading or unloading heavy cargo on a ship or dock.

Cringle A small reinforced loop or ring in the edge of a sail for attaching ropes or lines.

Crow’s Nest A lookout platform high on a mast where sailors watch for land, ships, or hazards.

Current The continuous, directed movement of seawater generated by wind, tides, or differences in temperature and salinity.

Cutter A small, single-masted sailing vessel rigged fore-and-aft, often used for patrol, rescue, or harbor duties.

Daggerboard A removable, vertical board that slides through a slot in the hull to reduce sideways drift and improve stability.

Davit A small crane-like device used to lower or raise boats, anchors, or heavy equipment over the side of a ship.

Dead Ahead Directly in front of the ship’s bow.

Dead Astern Directly behind the ship’s stern.

Dead Reckoning A navigation method that estimates a vessel’s position based on its previous location, speed, and course over time, without external references.

Deadweight (DWT) The total weight a ship can safely carry, including cargo, fuel, crew, and provisions.

Deck A flat surface or platform on a ship, serving as a floor for crew and equipment.

Deckhead The underside of the deck above; essentially, the ceiling of a ship’s compartment.

Deep Six A sailor’s slang term meaning to discard or throw something overboard.

Depth Sounder An instrument used to measure the depth of water beneath a vessel.

Derrick A lifting device made up of a mast and boom, used for loading and unloading cargo.

Deviation The error in compass reading caused by magnetic influences on board the ship.

Dew Point The temperature at which moisture in the air condenses into water droplets, important for weather and visibility forecasting.

Displacement The weight of water a vessel displaces when floating, equal to the vessel’s actual weight.

Displacement Hull A hull designed to move through the water by pushing it aside, rather than planing on top of it.

Ditty Bag A small bag used by sailors to keep personal tools, sewing gear, or small belongings.

Dock A structure where ships are moored for loading, unloading, or repairs.

Dockyard A facility where ships are built, maintained, or repaired.

Dogwatch A shorter watch period, usually divided into two two-hour shifts in the late afternoon, allowing crew rotation for meal times.

Dolphin A cluster of piles driven into the seabed, used as a mooring point or to mark a channel.

Dory A small, narrow, flat-bottomed boat traditionally used for fishing or as a ship’s tender.

Double Bottom A space between a vessel’s inner and outer bottom plating, used for ballast or as extra protection against grounding.

Draft (or Draught) The vertical distance between the waterline and the lowest part of the hull, showing how deep the vessel sits in the water.

Dredger A vessel designed to remove silt, sand, or debris from the seabed to keep waterways clear.

Drift The sideways movement of a vessel caused by wind, tide, or current.

Dripless Seal A watertight seal around the propeller shaft designed to prevent leaks into the hull.

Dry Dock A dock that can be drained of water to allow work on a ship’s hull below the waterline.

Dunnage Loose materials such as wood or mats placed around cargo to prevent shifting or damage during transport.

Duplex Chain A heavy-duty chain consisting of two linked rows for extra strength.

Duct Keel A narrow passage formed by the double bottom of a ship’s hull, used for running pipes and cables safely.

Ease Sheets To gradually let out a sail’s control line (sheet) to reduce wind pressure and slow the vessel’s speed.

Easting The progress made toward the east; used in navigation to measure or describe distance traveled eastward.

Ebb Tide The period when the sea level falls as the tide flows out toward the ocean.

Echo Sounder An electronic device that measures water depth by sending sound waves to the seabed and timing their return.

Earrings Short ropes or lines used to secure the top corners of large sails to the yardarms, essential for adjusting and fastening sails.

Embayed A situation where a vessel is trapped between two headlands with onshore winds, making navigation difficult and potentially dangerous.

Engine The power source that drives a vessel, available in various types and sizes depending on the ship’s design and purpose.

Ensign The national flag flown by a vessel to show its country of registration.

EP (Estimated Position) A navigational term referring to a vessel’s approximate location, calculated from course, speed, and time when exact positioning tools are unavailable.

EPIRB (Emergency Position Indicating Radio Beacon) A vital safety beacon that automatically transmits a distress signal with the ship’s location to satellites, aiding in rescue operations.

ETA (Estimated Time of Arrival) The projected time when a vessel is expected to reach its destination, based on current speed and route.

ETD (Estimated Time of Departure) The scheduled or planned time when a vessel is expected to leave port or its current location.

Estuary A coastal waterway where a river meets the sea, influenced by both tides and freshwater currents.

Even Keel When a vessel is perfectly balanced in the water, neither leaning to one side nor trimmed by the bow or stern, ensuring smooth and stable movement.

Extremis A critical situation in navigation when two vessels are in immediate danger of collision and must take last-moment action to avoid impact.

Eye Bolt A strong metal bolt with a circular loop at one end, used to attach ropes, cables, or lifting equipment.

Eye of the Wind The exact direction from which the wind blows; a sailing vessel cannot make headway when facing directly into it.

Eye Splice A ropework technique used to form a secure, permanent loop at the end of a rope by weaving its strands back into itself.

Fairlead A deck or hull fitting that guides ropes or lines smoothly, reducing friction and preventing wear.

Fairway A safe, navigable channel in a harbor, river, or coastal area, clear of obstructions for ships to pass through.

Fathom A nautical unit of measurement used to express water depth, equal to six feet.

Fathometer An instrument that measures the depth of water beneath a vessel, commonly known as an echo sounder.

Fender A cushioning device, often made of rubber, foam, or air-filled material, placed between a vessel and a dock or another ship to prevent damage.

Figurehead An ornamental carved figure placed at the bow of older sailing ships, traditionally symbolizing the vessel’s spirit or name.

Fireboat A specialized vessel equipped with powerful water pumps and firefighting gear, used to combat fires on ships or along waterfront areas.

Fireship A historical naval weapon—an unmanned ship loaded with explosives or combustibles, set on fire and directed toward enemy fleets.

First Mate The deck officer second in command to the captain, responsible for cargo operations, deck crew, and day-to-day vessel management.

First Rate An old naval term describing the largest class of warships from the 17th to 19th centuries, typically carrying over 100 guns.

Flag Hoist A communication method using signal flags strung together to transmit coded messages between ships.

Flag Officer A senior naval commander entitled to fly a distinguishing flag on their ship, such as an admiral or vice admiral.

Flare A visual distress signal that produces a bright light or flame, used to attract attention during emergencies at sea.

Fleet A group of ships sailing together under common command, ownership, or purpose, such as a naval or commercial fleet.

Flotsam Floating debris or wreckage from a ship, often referring to cargo or equipment lost overboard but still adrift.

Fluke The broad, wedge-shaped end of an anchor’s arm designed to dig into the seabed and hold the vessel in place.

Fo’c’sle (Forecastle) The forward section of a ship, traditionally housing crew accommodations or storage.

Fore A term meaning toward the front or bow of a vessel.

Fore and Aft Running lengthwise along the vessel, from the bow (front) to the stern (rear).

Foremast The mast located nearest the bow on ships with two or more masts.

Foresail The lowest sail on the foremast of a square-rigged ship; on a fore-and-aft rigged vessel, the sail set ahead of the mainmast.

Forward Toward the front or bow of a ship.

Freeboard The vertical distance from the waterline to the top edge of the deck, showing how high the vessel sits above water.

Furl To neatly roll or wrap a sail around a spar, boom, or mast to secure it when not in use.

Full and By A sailing condition where the vessel is close-hauled—sailing as near the wind as possible—while keeping the sails filled for maximum speed.

Gaff A spar that supports the upper edge of a fore-and-aft sail, commonly used in traditional sailing rigs to shape and control the sail.

Galley The kitchen area of a vessel, fitted with cooking equipment and storage for preparing meals at sea.

Galley Slave A person, historically a prisoner or captive, forced to row a galley ship by hand during the 16th to 19th centuries.

Gangplank A movable bridge or ramp used to board or disembark from a vessel, especially when docked at a pier.

Gangway An opening in the ship’s side or bulwark that allows entry or exit; also a command used to tell people to clear the passage.

Garboard The lowest plank or plate on a boat’s hull, running next to the keel and vital to the hull’s strength and watertightness.

Garboard Strake The first strake (row of planking or plating) laid alongside the keel, forming the foundation for the rest of the hull.

Gasket A cord or strip of canvas used to tie up and secure a sail once it has been furled on the yard or boom.

General Average A maritime law principle requiring all parties involved in a voyage—ship, cargo, and freight—to proportionally share losses when part of the ship or cargo is intentionally sacrificed to save the rest in an emergency.

Genoa A large, overlapping foresail or jib that extends past the mast, designed to increase sail area and performance in light to moderate winds.

Gig A narrow, lightweight boat built for speed and ease of handling, often used to transport officers or crew between ship and shore.

Gimbal A pivoted mounting that allows an object, such as a compass or stove, to remain level despite the motion of the vessel.

Give-Way Vessel The vessel required by navigation rules to yield or maneuver to avoid a collision with another vessel.

Globe Valve A type of valve used in shipboard piping systems to regulate or stop the flow of liquid through a pipeline.

Gooseneck A flexible joint connecting the boom to the mast, allowing the boom to pivot freely both vertically and horizontally.

GPS (Global Positioning System) A satellite-based navigation system providing accurate global location, speed, and time data, essential for modern maritime navigation.

Grab Rails Sturdy handholds fixed to the deckhouse or cabin sides, giving crew members stability and safety when moving around the vessel.

Grapeshot A historical naval munition consisting of a cluster of small iron balls packed into a canvas bag, fired to damage rigging or personnel rather than ships themselves.

Ground Tackle A collective term for all anchoring gear, including anchors, chains, cables, and associated fittings.

Gudgeon and Pintle The interlocking hinge fittings that attach a boat’s rudder to its sternpost, allowing smooth steering movement.

Gunkholing Leisure cruising in shallow or sheltered waters, exploring quiet coves, bays, and inlets often unreachable by larger vessels.

Gunwale (pronounced “gunnel”) The upper edge or rim of a boat’s side, providing strength and structural support to the hull.

Guy A line or rope used to control and steady a spar or sail, preventing unwanted swinging or movement.

Gybe (or Jibe) A sailing maneuver in which the stern passes through the wind, shifting the boom and sails from one side to the other while sailing downwind.

Halyard (or Halliard) A line used to hoist or lower a sail, spar, or flag. It plays a key role in sail control and adjustment.

Hammock A canvas or fabric bed suspended from the deckhead, traditionally used by sailors as sleeping quarters at sea.

Hand Bomber An older term for ships that required crew to manually shovel coal into boilers to power steam engines.

Hand over Fist A phrase meaning rapid or steady progress, originally describing a sailor climbing rigging or hauling in rope.

Handsomely A command meaning to move slowly and carefully, often used when handling ropes or performing delicate maneuvers.

Hank A small fitting used to attach the edge of a sail to a stay, usually featuring a clip or snap that allows quick fastening and release.

Harbor (or Harbour, Haven) A naturally protected or man-made shelter where ships can safely anchor or dock, shielded from rough seas and weather.

Haul Wind To sail as close to the wind direction as possible, typically resulting in slower forward progress.

HAT (Highest Astronomical Tide) The highest predicted tide level that can occur under normal weather conditions, based on astronomical influences.

Hatch An opening in a ship’s deck providing access to compartments or cargo spaces below.

Hawse-hole A circular opening in the bow through which anchor chains or cables pass.

Hawsepiper A seafarer who has advanced to officer rank through practical experience rather than formal maritime education.

Head The toilet area on a ship, traditionally located near the bow where water flow could carry away waste.

Head of Navigation The farthest point upstream on a river that remains navigable for ships.

Head-to-Wind A position where the vessel’s bow faces directly into the wind, causing sails to lose power and luff.

Headfoil A streamlined sleeve or extrusion fitted over the forestay, designed with grooves to hold and guide the luff of a headsail.

Heads Another term for the toilets on board a ship.

Headsail Any sail set forward of the foremost mast, including jibs and genoas, used to enhance steering and speed.

Headway The forward motion or progress of a vessel through the water.

Heave The up-and-down motion of a ship caused by waves or swells.

Heave Down To tilt or careen a vessel onto its side, often for maintenance, cleaning, or hull repairs.

Heave-to A sailing maneuver used in strong winds where the sails and rudder are positioned to stop forward movement and maintain stability.

Heaving to The act of stopping a sailing vessel by setting sails and helm against each other, allowing it to drift slowly leeward.

Heel The action of a vessel leaning or tipping to one side, usually due to wind pressure on the sails.

Heeling The continuous leaning of a sailing vessel as wind fills the sails, affecting balance and trim.

Helm The steering apparatus of a ship, including the wheel or tiller, used to control direction.

Helmsman The crew member responsible for steering the vessel and following navigational commands.

Hogging (or Hog) A structural distortion where the ship’s hull bends so the bow and stern sit lower than the midsection.

Hold The lower part of a vessel used for stowing cargo, supplies, or equipment.

Holiday A missed or thinly covered spot during painting or coating work on a vessel’s surface.

Holystone A soft sandstone block used with water and sand to scrub and clean wooden decks.

Horn A sound-producing device powered by electricity or compressed air, used for signaling or warnings at sea.

Horse A metal or wooden fitting that provides an attachment point for controlling sheets or tackle on deck.

Hounds Fittings on a mast that secure and support the upper ends of shrouds or stays.

Hull The main body or structural framework of a vessel that provides buoyancy and shape.

Hydrofoil A type of high-speed boat with wing-like foils beneath the hull that lift it above the water as it moves, reducing drag and increasing efficiency.

Icebreaker A specially reinforced ship designed to break through ice-covered waters, allowing safe passage for vessels in polar or frozen regions.

Icing A dangerous condition where seawater spray freezes upon contact with a ship’s structure in very low temperatures, typically below -10°C and strong winds, increasing weight and instability.

Idlers Crew members not assigned to regular watch duties, often skilled specialists such as carpenters, sailmakers, or cooks.

IMO (International Maritime Organization) A United Nations agency responsible for setting global standards for the safety, security, and environmental performance of international shipping.

Impeller A rotating blade or disc used in pumps or engines to move water or air, essential for cooling systems and propulsion.

In Irons A sailing condition where a vessel’s bow points directly into the wind, causing the sails to lose power and the boat to stall.

In the Offing Originally referring to the area of sea visible from a ship, it now means something expected or about to occur soon.

Inboard Motor An engine mounted within the hull of a boat, typically below the deck, providing propulsion through a fixed shaft and propeller.

Inboard-Outboard Drive System Also known as a sterndrive, this hybrid propulsion system combines features of inboard and outboard engines, offering power and maneuverability for larger boats.

Inclinometer An onboard instrument that measures the tilt or lean of a vessel, indicating how far it is heeling or rolling.

International Date Line An imaginary line running roughly along the 180° meridian, marking the point where calendar days change when crossed eastward or westward.

International Maritime Law A collective framework of global laws, conventions, and treaties that regulate maritime trade, navigation, and conduct between nations.

International Waters Ocean areas that lie beyond any nation’s territorial boundaries, open to all countries for navigation and lawful use.

IRPCS (International Regulations for Preventing Collisions at Sea) A globally recognized set of rules that define how vessels should navigate to avoid collisions and ensure safety at sea.

Isobars Lines drawn on weather charts connecting areas of equal air pressure, helping mariners interpret wind patterns and forecast conditions.

Isobath Contour lines on nautical charts connecting points of equal depth, used to visualize underwater terrain and ensure safe passage.

ITF (International Transport Workers’ Federation) A global federation representing transport industry workers, including seafarers, advocating for fair labor rights and working conditions worldwide.

ITU (International Telecommunication Union) A specialized United Nations agency that coordinates global communication systems, including radio frequencies and maritime communication standards.

Jack A flag flown from the jackstaff at the bow of a ship, typically indicating nationality or signal status; informally, the term also refers to a sailor.

Jack Tar A traditional nickname for a sailor, dating back to the age of sail, often referring to those dressed in square-rig uniforms and wearing tarred pigtails.

Jacklines or Jack Stays Safety lines running along both sides of a vessel from bow to stern, allowing crew members to clip on harnesses for secure movement on deck in rough conditions.

Jacob’s Ladder A rope ladder fitted with wooden rungs, used for climbing up or down the side of a ship, especially when boarding from smaller boats.

Jetsam Cargo or goods intentionally thrown overboard to lighten a ship in distress, often to improve stability or buoyancy.

Jetty A structure extending from the shore into a body of water, built to protect harbors, control currents, or serve as a docking point for ships.

Jettison To throw cargo, equipment, or stores overboard in an emergency to stabilize or lighten a vessel.

Jib A triangular sail set ahead of the foremast, attached to the forestay, used to balance the mainsail and aid maneuverability.

Jibboom A spar that extends forward from the bowsprit, allowing additional headsails to be rigged for improved sail area and performance.

Jibe (or Gybe) A sailing maneuver in which the stern passes through the wind, causing the mainsail to shift from one side to the other while sailing downwind.

Jigger-Mast The fourth and smallest mast on a sailing ship, typically located at the stern on vessels with multiple masts.

Jolly Boat A small, light workboat or tender carried aboard larger ships, used for transport between ship and shore.

Jollies A traditional Royal Navy term referring to the Royal Marines.

Jonah A person believed to bring bad luck to a ship or crew, based on old maritime superstition.

Junk Old or worn-out ropes and rigging aboard a ship, often reused by unlaying the strands to make oakum for sealing joints.

Jury A term describing a temporary or makeshift replacement for damaged or lost equipment aboard a vessel, such as a jury mast or rudder, used in emergencies.

Keel The central structural backbone of a vessel running along the bottom of the hull from bow to stern, providing strength, stability, and balance in the water.

Keelhauling An old naval punishment in which a sailor was dragged beneath the ship’s keel, often resulting in severe injury or death; now a historical term symbolizing extreme discipline.

Keelson (or Kelson) A sturdy timber or beam laid above the keel inside a wooden ship, reinforcing the hull and enhancing its longitudinal strength.

Kedge A small, lightweight anchor used for repositioning or maneuvering a vessel in confined areas, often set out by a smaller boat and hauled in to move the ship.

Ketch A two-masted sailing vessel with a mainmast and a smaller mizzenmast positioned ahead of the rudder post, commonly used for cruising and fishing.

Kicking Strap (or Boom Vang) A tackle or line used to pull the boom downward, maintaining sail shape and control, particularly when sailing downwind or on a reach.

Killick A small anchor, often symbolic in the Royal Navy to denote a leading seaman; colloquially used to describe a sailor skilled in anchor work.

King Plank The central plank running along the middle of a ship’s deck, serving as the main structural piece from which other deck planks are fitted.

Kingpost A strong vertical post used to support decks or rig cargo handling equipment, providing stability for lifting and loading operations.

Kissing the Gunner’s Daughter A historic naval punishment where a sailor was bent over a cannon and flogged, symbolizing strict discipline aboard early naval ships.

Kite A slang term for a spinnaker, a large, lightweight sail used to capture wind when sailing downwind for maximum speed.

Knee An angled or curved piece of timber or metal fitted inside a ship’s hull to strengthen the joint between the deck beams and the sides.

Knarr A sturdy Norse merchant ship from the Viking Age, designed for long voyages across open seas, carrying cargo and goods between settlements.

Knot A unit of speed measurement equal to one nautical mile per hour, used universally in navigation and maritime communication.

Knotmeter An instrument that measures a vessel’s speed through the water in knots, often using a paddlewheel or electronic sensor.

Know the Ropes A phrase meaning to be fully experienced and knowledgeable about handling ropes and sails—originating from the skills required aboard traditional sailing ships.

Knuckle A noticeable angle or abrupt curve in a ship’s hull or deck, marking a change in contour or structure.

Ladder On ships, stairways are typically called ladders. They are usually narrow and steep, designed for compact, vertical movement between decks.

Laker A vessel built and operated exclusively on the Great Lakes, designed to navigate freshwater trade routes and locks.

Land Lubber A term for someone unfamiliar with life at sea, often used humorously by sailors to describe those inexperienced with maritime ways.

Lanyard A short line or cord used to fasten, secure, or tether objects such as tools, keys, or whistles to prevent them from being lost overboard.

Larboard An old term for the left side of a ship, now replaced by “port” to avoid confusion with “starboard.”

Large (By and Large) A nautical phrase meaning sailing both with and against the wind; now commonly used to mean “in general” or “on the whole.”

Latitude The angular distance measured north or south of the equator, expressed in degrees and used to determine a vessel’s position.

LAT (Lowest Astronomical Tide) The lowest predictable tide level under normal weather conditions, used as a baseline reference on nautical charts.

Lateral System A standardized system of navigation buoys and markers that indicate the port and starboard sides of navigable channels.

Launch To place a vessel in the water for the first time; also refers to a small, open motorboat used for transport or harbor duties.

Lay A command directing the movement of crew or the course of the ship; also refers to the direction in which rope strands are twisted.

Lay Down The initial stage of ship construction, when the keel is laid in the shipyard to begin the building process.

Lazy Jacks Lines rigged from the mast to the boom that help catch and control a sail as it is lowered or reefed, making sail handling easier.

League A traditional nautical distance measurement, typically equal to three nautical miles.

Lee The side of a vessel sheltered from the wind, offering protection from weather and waves.

Lee Helm The tendency of a vessel to turn away from the wind, requiring corrective steering toward the leeward side to maintain course.

Lee Shore A shore onto which the wind is blowing, dangerous for ships as it increases the risk of being driven aground.

Leech The trailing edge of a sail, extending from the head to the clew, often adjusted to control sail shape and reduce twist.

Leeward The direction away from the wind; opposite of windward.

Leeway The sideways drift of a vessel off its intended course due to wind pressure on the hull and sails.

Let Go and Haul A sailing order meaning to adjust the sails and align the vessel with the direction of the wind.

Letter of Marque and Reprisal A government-issued license authorizing private vessels, known as privateers, to capture enemy ships during wartime.

Lifeboat A small, durable boat carried aboard larger ships for emergency evacuation and rescue operations.

Lifeline A safety cable or line running along the deck or rail of a boat to prevent crew from falling overboard.

Liferaft An inflatable, self-righting raft designed for emergency escape if a ship must be abandoned.

Line The proper nautical term for ropes used aboard ships, each named according to its specific function, such as halyard or sheet.

Liner Originally referring to large warships sailing in formation, now used for major passenger ships or cargo vessels operating on fixed routes.

List The permanent or temporary lean of a ship to one side caused by uneven loading or shifting weight.

Loaded to the Gunwales A phrase meaning a vessel is loaded up to the top of its sides, often used figuratively to describe someone as extremely drunk or overwhelmed.

Loggerhead An iron tool used in ship maintenance to drive caulking into seams; historically, also a weapon in quarrels between sailors.

Log An instrument for measuring a vessel’s speed through the water; also the written record of daily ship operations and navigation.

Logbook The official record of a ship’s voyage, documenting navigation data, weather conditions, crew activities, and significant events.

Longitude The angular distance east or west of the Prime Meridian, measured in degrees, essential for determining a ship’s global position.

Lookout A crew member assigned to keep watch for hazards, ships, or landmarks, often stationed high in the crow’s nest or on the bow.

Loose Cannon Originally an unsecured cannon rolling dangerously on deck; now used to describe an unpredictable or reckless person.

Lubber’s Hole An opening in the mast platform that allows sailors to climb onto the top without going through the rigging.

Lubber’s Knot A simple or clumsy knot, typically made by inexperienced sailors; often another name for a “granny knot.”

Lubber’s Line A fixed mark inside a compass case indicating the ship’s forward direction or heading.

Luff The leading edge of a sail that faces the wind; to “luff up” means steering the vessel’s bow closer to the wind.

Luffing The flapping of a sail when it loses wind pressure, signaling that the vessel is pointed too close to the wind.

Lying Ahull A storm tactic in which all sails are taken down and the vessel is left to drift freely with minimal steering, allowing it to ride out heavy seas safely.

MCA (Maritime and Coastguard Agency) The official organization in the United Kingdom responsible for regulating maritime safety, ship standards, and search and rescue operations.

MHWS (Mean High Water Springs) The average height of high tides during spring tide conditions, representing the highest regular tidal level.

MHWN (Mean High Water Neaps) The average height of high tides during neap tide conditions, slightly lower than spring high tides.

MLWS (Mean Low Water Springs) The average level of low tides during spring tides, marking the lowest regular tidal height.

MLWN (Mean Low Water Neaps) The average level of low tides during neap tides, higher than the spring low tides.

MMSI (Maritime Mobile Service Identity) A unique nine-digit number assigned to a vessel for identifying it in maritime radio and digital communications.

MV (Motor Vessel) A ship prefix denoting that the vessel is powered by engines rather than sails.

Magnetic Compass A traditional navigation tool that uses a magnetized needle to point toward magnetic north.

Magnetic Deviation An error in compass readings caused by magnetic interference from the ship’s own metal structures or equipment.

Magnetron A high-powered electronic device that generates microwaves, used in radar systems aboard ships for navigation and detection.

Mainbrace A line or tackle that controls the main yard of a sailing ship, crucial for maneuvering and adjusting sail positions.

Mainmast (or Main) The tallest and most important mast on a sailing vessel, supporting the main sails and carrying significant rigging.

Mainsheet A rope used to control the angle and tension of the mainsail, adjusting the boom’s position for optimal sail performance.

Man Overboard! An emergency call announcing that someone has fallen into the water, triggering immediate rescue procedures.

Man of War A heavily armed naval warship from the age of sail, built for combat and long-distance engagements.

Manifest An official document listing all cargo, passengers, and crew aboard a vessel, required for customs and port authorities.

Marina A harbor facility designed for small boats and yachts, providing mooring, fuel, maintenance, and leisure amenities.

Marine Insurance Insurance coverage protecting ships, cargo, and related transport operations from loss, damage, or other maritime risks.

Marine Salvage The recovery of a ship, its cargo, or other property after a wreck or maritime accident, often involving specialized equipment.

Mariner A general term for a sailor or seaman skilled in operating or navigating ships.

Marines (Soldiers Afloat) Members of the Royal Marines or naval infantry units, traditionally responsible for security and boarding operations aboard ships.

Marinized Engine An engine modified for marine use, equipped with corrosion-resistant components and a seawater cooling system.

Maritime Administration A government body overseeing national maritime affairs, from ship registration and training to policy and trade promotion.

Maritime Buoyage System A system of standardized buoys and markers used to guide navigation, mark hazards, and identify safe channels.

Maritime Domain Awareness The continuous understanding of activities in the maritime environment that could affect safety, security, trade, or ecology.

Maritime Law A collection of international and national laws that govern navigation, shipping, commerce, and offenses occurring at sea.

Maritime Pilot A professional navigator with expert local knowledge who assists ships entering or leaving ports or navigating tricky waterways.

Maritime Safety All measures, standards, and practices designed to prevent accidents at sea and protect life, property, and the marine environment.

Maritime Security Protection of maritime interests from unlawful acts such as piracy, smuggling, and terrorism at sea.

Marlinspike A pointed metal tool used by sailors to separate strands of rope or wire for splicing and knot work.

Marconi Rig A modern sail rigging system featuring tall, slender masts and triangular sails, resembling a radio antenna.

Mast A vertical pole on a vessel supporting sails, rigging, and signaling equipment, fundamental to sailing ship structure.

Mast Step The reinforced base or socket in the keel or deck where the mast is fixed to provide firm support.

Masthead The top section of a mast, often used for lookout duties, rigging attachments, or mounting lights and instruments.

Master The captain or commanding officer of a commercial vessel, responsible for navigation, crew management, and vessel operations.

Master-at-Arms A naval officer charged with enforcing discipline, maintaining order, and overseeing shipboard security.

Mate An officer ranking below the master, responsible for navigation, cargo handling, and crew supervision.

Matelot A traditional Royal Navy term meaning “sailor,” borrowed from the French word for shipmate.

Mayday An international distress signal used in voice radio communications to indicate a life-threatening emergency.

Measured Mile A fixed nautical distance used to test a ship’s speed and performance, usually marked by visible shore indicators.

Mercator Projection A navigational map projection developed by Gerardus Mercator in 1569, showing lines of constant compass bearing as straight lines.

Meridian An imaginary line encircling the Earth from pole to pole, used to measure longitude in navigation.

Mess A dining area aboard a ship where crew members eat; the term also refers to the group sharing meals together.

Mess Deck Catering A naval system where a group of crew members collectively manage meal preparation and expenses.

Midshipman A junior naval officer in training, often serving as an apprentice navigator or future commissioned officer.

Mizzen The smaller mast located aft on a ketch or yawl; also refers to the sail set on that mast.

Mizzen Staysail A lightweight sail hoisted between the mizzenmast and mainmast, used in moderate winds for better downwind speed.

Mizzenmast (or Mizzen) The third mast on larger sailing vessels, positioned behind the mainmast and supporting the mizzen sail.

Monkey Fist A ball-shaped knot made by wrapping a rope around itself, often weighted and thrown to pass a line between ship and dock.

Moor To secure a ship or boat to a fixed point, such as a dock, buoy, or anchor.

Mooring The act or method of fastening a vessel to a stationary object; also the system of ropes, chains, and anchors used.

Mooring Buoy A floating device anchored to the seabed, designed for vessels to tie onto instead of anchoring directly.

Mooring Line A rope or cable used to fasten a ship securely to a dock, quay, or buoy.

Motorboat A small vessel powered by an internal combustion engine, commonly used for leisure, transport, or short-distance travel.

Mutiny A deliberate revolt by a ship’s crew against lawful authority, often during harsh conditions or disputes at sea.

Muster The organized assembly of crew or passengers for roll call, drills, or emergency briefings.

Muster Station A designated safe area aboard a ship where passengers and crew gather during an emergency for instructions and evacuation.

Naval Architecture The discipline combining engineering and design to create ships and other floating structures, ensuring they are safe, stable, and efficient at sea.

Navigation The science and practice of determining a vessel’s position and directing its movement safely from one location to another.

Navigation Lights The colored lights displayed by vessels during nighttime or low-visibility conditions to signal their position, direction, and type of activity to nearby ships.

Navigation Rules A set of internationally recognized maritime guidelines—often called “rules of the road”—that prevent collisions and determine right-of-way responsibilities at sea.

Nautical Almanac An annual publication containing essential astronomical data, such as the positions of the sun, moon, and stars, used for celestial navigation.

Nautical Chart A detailed map depicting coastal regions, water depths, hazards, and navigational aids, used by mariners for route planning and safe navigation.

Nautical Dawn The time in the morning when the sun is 12 degrees below the horizon, marking the start of nautical twilight and sufficient light for navigation.

Nautical Dusk The evening period when the sun is 12 degrees below the horizon, signaling the end of nautical twilight and the onset of full darkness.

Nautical Mile A standardized unit of distance used in marine and air navigation, equal to approximately 1.852 kilometers or 1.15078 land miles.

Nautical Twilight The period before sunrise and after sunset when the sun lies between 6 and 12 degrees below the horizon, providing enough light to discern the horizon line for navigation.

Neap Tide A moderate tide occurring during the first and third quarters of the moon, when the gravitational forces of the sun and moon partially cancel each other, resulting in minimal tidal range.

Neptune The Roman god of the sea, often invoked in maritime folklore and ceremonies to bless sailors and ships before voyages.

Net Tonnage A measurement expressing a vessel’s cargo-carrying capacity, derived by subtracting non-revenue spaces such as crew quarters and machinery rooms from the gross tonnage.

Night Orders Written instructions left by the ship’s captain for officers on duty overnight, outlining navigation plans and operational precautions.

Nipper A short length of rope used to fasten an anchor cable to a messenger line, helping to manage heavy anchor chains during raising or lowering operations.

No Room to Swing a Cat A phrase originating from the age of sail, referring to cramped shipboard quarters where there wasn’t enough space to use the “cat-o’-nine-tails” whip; now used to describe any tight or crowded area.

Nun Buoy A red, conical buoy marking the starboard (right-hand) side of a navigable channel when a vessel is returning from the sea toward harbor.

Oar A long wooden pole with a flat blade at one end, used to row or propel a boat manually through the water.

Offing The part of the sea visible from shore but lying beyond the anchoring area; a ship “in the offing” is sailing at a moderate distance from land.

Oilskin Waterproof outerwear made from treated fabric, worn by sailors to stay dry during rough weather and heavy sea spray.

Old Man A friendly, traditional nickname for the ship’s captain or master, commonly used among crew members.

On the Rocks A phrase describing a ship that has run aground on rocks, often resulting in damage; also used figuratively to mean in trouble.

On the Wind A sailing term meaning to steer as close as possible to the direction from which the wind is blowing, also known as “close-hauled.”

Ordinary Seaman The entry-level rank for a deckhand, responsible for routine duties such as cleaning, maintenance, and assisting with ship operations.

Orderbook A record of confirmed shipbuilding orders held by shipyards, used to track construction activity and demand trends in the maritime industry.

Oreboat A bulk carrier designed primarily for transporting iron ore, especially across the Great Lakes.

Orlop Deck The lowest deck of a ship, located above the hold, traditionally used for storing cables, spare gear, and provisions.

Outboard Motor A self-contained engine attached externally to the stern of a boat, providing propulsion and steering for smaller vessels.

Outfall The outlet where a river, drain, or sewer discharges into the sea or another body of water.

Outhaul A control line used to stretch the foot of a sail along the boom, adjusting its shape for better performance.

Outward Bound A term for a vessel departing from port, heading toward open waters or its next destination at sea.

Overall Length (LOA) The total length of a vessel measured from the tip of the bow to the stern’s furthest point, excluding fittings such as bowsprits.

Overbear To sail downwind directly toward another vessel, often disrupting its wind and affecting its ability to maneuver.

Overboard Refers to anything or anyone that goes over the side of a vessel and into the water.

Overfall A patch of turbulent, breaking waves created when strong currents meet opposing winds or underwater obstacles.

Overhaul The act of inspecting, maintaining, and repairing ship machinery or sails; in sailing, to haul buntlines over sails to prevent wear.

Overhead The nautical term for a ship’s ceiling, which is actually the underside of the deck above.

Overreach A sailing mistake in which a vessel continues its tack too long, causing it to sail past the optimal turning point.

Over the Barrel An old naval punishment method involving flogging over a cannon barrel; now used to describe being trapped in a difficult position.

Overwhelmed A situation where a vessel is overpowered by wind or waves, leading to capsizing or sinking.

Owner A term once used in the Royal Navy for a ship’s captain, originating from a time when captains often personally owned their vessels.

Ox-Eye A small, ominous cloud that can signal the approach of a storm; often regarded by sailors as a warning of bad weather ahead.

Packet Boat A vessel that operates on a regular schedule, carrying mail, cargo, and passengers between ports—an early form of scheduled maritime transport.

Painter A rope attached to the bow of a small boat, used to secure or tow it to another vessel or dock.

Panpan A radio call indicating urgency but not immediate danger; used when help is needed but there’s no threat to life or the vessel.

Parbuckle A lifting method where a rope is looped around a cylindrical object, allowing it to be rolled up or lowered safely.

Parrel A movable collar or loop that holds a yard or gaff close to the mast, allowing it to slide easily when adjusting sails.

Part Brass Rags An old naval phrase meaning to end a friendship or quarrel, derived from sailors who shared brass cleaning rags until they fell out.

Passerelle A narrow bridge or gangway used for boarding or disembarking a vessel, often seen on modern yachts and cruise ships.

Pay To fill a seam with tar or pitch to make it watertight; can also mean to grease or oil rigging to protect it from wear.

Pay Off To release a crew from duty and settle their wages after a voyage; also used when a ship’s bow turns away from the wind.

Paymaster The naval officer in charge of handling payments, wages, and supplies on a ship.

Peak The uppermost corner of a four-sided sail or the highest point of a structure or mountain.

Pier A raised structure built out into the sea or river, used as a landing stage for ships, or as a promenade.

Pier-head Jump A last-minute assignment given to a sailor just before a ship departs—often unexpected and rushed.

Pilot A skilled navigator who guides ships through difficult or congested waters such as harbors or river mouths.

Pilot Boat A small, fast vessel that transports maritime pilots to and from ships entering or leaving port.

Pilot Ladder A rope ladder with wooden rungs, used by pilots and crew for boarding or leaving ships at sea.

Pilothouse The enclosed area from which a vessel is steered and navigated; also called the wheelhouse.

Pilotage The act or skill of navigating a vessel through narrow or busy waterways, usually under the direction of a pilot.

Pirate A sea robber who attacks and plunders ships without legal authority.

Pipe (Bos’n’s Call) A special whistle used by the boatswain to issue commands or ceremonial signals aboard ship.

Pipe Down A traditional command signaling the end of the day aboard ship—time for silence and lights out.

Piping the Side A formal naval salute made using the boatswain’s pipe to honor distinguished visitors boarding or leaving the ship.

Pitch The up-and-down movement of a ship’s bow and stern as it rides over waves; also refers to the angle of a propeller’s blades.

Pitching The repeated rise and fall of a vessel’s bow and stern in response to wave motion.

Pitchpole To capsize end over end, usually when a boat’s bow digs into a wave while moving fast.

Plank Owner A sailor who was part of a ship’s original commissioning crew—often seen as a badge of pride.

Planing When a vessel moves fast enough to skim along the water’s surface, lifted by hydrodynamic forces rather than buoyancy.

Plimsoll Line A marking on a ship’s hull showing the maximum safe loading level under various water conditions.

Points of Sail The different angles between a sailing vessel’s course and the direction of the wind, such as close-hauled, beam reach, and running.

Pontoon A flat-bottomed float or vessel used to support docks, bridges, or serve as a floating platform.

Poop Deck The raised deck at the rear of a ship, forming part of the roof of the cabin or superstructure.

Pooped Overtaken by a large following wave that washes over the stern; also means extremely tired or worn out.

Port The left-hand side of a ship when facing forward, marked with a red navigation light at night.

Port Authority The administrative body managing the operations, security, and infrastructure of a port.

Port Bow The front left section of a ship when facing forward.

Port Hole A circular window in a ship’s hull, allowing light and air into cabins or compartments.

Portlight A window fitted into a vessel’s side that can usually be opened for ventilation.

Port of Call A harbor where a ship stops during its voyage to load or unload goods or take on passengers and supplies.

Port Quarter The rear left-hand section of a vessel when facing forward.

Port Side The entire left-hand side of a vessel when facing the bow.

Port Tack A sailing condition where the wind blows onto the port side and the mainsail lies to starboard.

Port Watch The crew team assigned to the port side during their duty period on a watch rotation.

Position Line (Line of Position) A line drawn on a nautical chart to indicate a vessel’s possible position, determined through navigation readings or celestial sights.

Press Gang Groups historically used, especially by the Royal Navy, to forcibly recruit men into naval service.

Preventer (Gybe or Jibe Preventer) A safety line used to restrain or control the boom during a jibe, preventing accidental movement.

Privateer A privately owned ship authorized by a government to attack enemy vessels during wartime.

Propeller A rotating device with blades that drives a vessel forward by converting engine power into thrust.

Propeller Shaft The long shaft connecting the engine to the propeller, transmitting power for propulsion.

Propeller Walk (Prop Walk) The sideways motion of a boat’s stern caused by the rotation of the propeller, affecting how it turns.

Prow A poetic or literary term for the front part of a ship, also called the bow.

Pulley A wheel with a grooved rim that changes the direction of a rope or cable; widely used in a ship’s rigging.

Pulpit A safety rail or guard at the bow, protecting crew working on the foredeck.

Pushpit A guardrail at the stern, offering safety and support for mounting navigation gear or lifebuoys.

Pusser Naval slang for the ship’s purser—the officer responsible for provisions, stores, and supplies.

Put About To change a sailing vessel’s course by turning its bow through the wind; also called tacking.

Pyrotechnics Flares or fireworks used at sea for signaling distress, celebrations, or visual communication.

Quadrant A historical navigational instrument used to measure angles up to 90 degrees. It was vital for celestial navigation before the advent of sextants and modern positioning systems.

Quarantine A mandatory isolation period for ships arriving in port to prevent the spread of infectious diseases. The term also refers to the designated area where such vessels are held until cleared.

Quarter The section of a ship located between the beam and the stern, roughly one-fourth of the vessel’s length from the rear.

Quarterdeck Traditionally, the aft deck of a naval vessel reserved for officers and ceremonial duties. It serves as a place of command, honor, and formal activity.

Quartering Sea A wave pattern where the sea strikes the vessel from an angle between the stern and the beam, often causing both rolling and pitching motions.

Quartermaster A naval specialist responsible for steering, maintaining course, and managing navigational signals. On merchant ships, this role assists the officer of the watch in steering duties.

Quarters The designated living spaces aboard a ship for officers and crew. The term also applies to specific duty stations during drills or emergencies, such as “battle stations.”

Quay (or Quayside) A solid platform or structure built along the shore for mooring, loading, and unloading ships. Similar in purpose to a dock but usually constructed of stone or concrete.

Queen’s (or King’s) Regulations A set of formal rules and guidelines governing the conduct, discipline, and organization of the Royal Navy, issued under the authority of the reigning monarch.

Quick Flashing Light A navigational light that flashes at least sixty times per minute, commonly used on buoys and lighthouses to mark hazards or guide mariners safely.

Raft A flat floating platform made from buoyant materials or inflatable tubes, used for transport, rescue, or survival at sea. In maritime terms, it often refers to a life raft designed for emergency use.

Radar Short for Radio Detection and Ranging, a system that detects and tracks objects by bouncing radio waves off them—essential for modern navigation and collision avoidance.

Radar Beacon (Racon) A transponder beacon that responds to radar signals by sending back a coded signal, helping ships determine their exact bearing and range.

Radar Reflector A passive device that increases a vessel’s visibility on radar screens by reflecting radar waves, especially important for small craft.

Radio Direction Finder (RDF) A navigational tool that determines the direction of a radio signal source, aiding in position fixing and course plotting.

Ram A reinforced section at the bow of a ship designed for striking enemy vessels—an ancient but once-effective naval weapon.

Range (1) In navigation, an alignment of two markers or lights that guides a vessel safely through a channel. (2) The vertical difference between high and low tide. (3) The visible distance of an object or light.

Range Finder An optical or electronic device used to calculate the distance from the observer to an object, crucial for navigation and naval gunnery.

Range Lights A pair of navigational lights placed in line to help vessels maintain a safe course along a channel’s centerline.

Ratlines Rope steps attached horizontally between a ship’s shrouds, forming ladders for sailors to climb the rigging and access sails.

Rating An enlisted sailor classified by their rank or specialization, such as boatswain’s mate or gunner’s mate.

Rations The controlled distribution of food and provisions aboard a ship—especially vital on long voyages where supplies were limited.

Reach A sailing direction between close-hauled and running, where the wind comes from the side or quarter of the vessel. Includes close, beam, and broad reaches.

Reef (1) To reduce the area of a sail during strong winds by folding or rolling part of it. (2) A submerged ridge of rock or coral that poses a navigational hazard.

Reef Knot Also known as a square knot, this simple and secure knot is used to tie two ropes together neatly.

Reef Points Short cords attached to sails, allowing them to be tied up when reefing to reduce sail area.

Reef-Bands Extra canvas strips sewn across sails at the reefing points to reinforce them against tearing.

Reef-Tackles Lines and blocks used to pull up and secure the reefed portion of a sail during heavy weather.

Reefing Pennant A strong rope used to haul down the reef cringle to the boom when shortening sail.

Reduced Cat A smaller version of the cat-o’-nine-tails whip, historically used in the Royal Navy for disciplining younger crew members.

Red Duster A nickname for the British Civil Red Ensign—the flag flown by British merchant vessels worldwide.

Register Ton A measurement of internal ship volume equal to 100 cubic feet, used in calculating a vessel’s tonnage.

Relative Bearing The direction to an object measured clockwise from the ship’s bow, rather than from true or magnetic north.

Righting Couple The balancing force that returns a heeled ship to an upright position, determined by the ship’s center of gravity and buoyancy.

Rig The configuration of a ship’s masts, sails, and rigging. Common types include sloop, ketch, and schooner.

Rigging The system of ropes, cables, and chains that support a ship’s masts and control its sails. Divided into standing rigging (fixed) and running rigging (movable).

Rigging Screw Also called a turnbuckle, it’s a device used to adjust the tension of standing rigging or stays.

Rigol A raised rim or lip above a porthole designed to deflect rain and spray away from the opening.

Roach The outward curve along the leech (trailing edge) of a sail that increases sail area and improves performance.

Roll The side-to-side rocking motion of a ship around its longitudinal axis, often caused by waves or wind.

Rolling Tackle A system of ropes and pulleys used to steady the yards during rough seas and reduce excessive rolling.

Rope’s End A short piece of rope historically used for minor punishment or quick utility jobs aboard ship.

Rudder A flat blade mounted at a ship’s stern used for steering by redirecting water flow.

Rudder Post The vertical shaft that connects the rudder to the tiller or steering gear, allowing it to pivot.

Rudder Stock The main shaft supporting the rudder and transmitting movement from the helm to the blade.

Rummage Sale Originally the sale of damaged or unclaimed cargo after unloading; now refers to any second-hand sale.

Run To sail directly before the wind, with sails fully extended for maximum speed.

Running Rigging The movable part of a vessel’s rigging used to adjust sails, including halyards, sheets, and control lines.

The Ropes The collective term for all lines aboard a ship. To “know the ropes” means being experienced in ship handling and operations.

Sagging:

When a wave’s trough lies amidships, causing the ship’s center to bend downward—a natural stress in heavy seas.

Sail-plan:

A detailed drawing showing different sail setups suited for various wind and sea conditions.

Sailing Certification:

An official document confirming a sailor’s knowledge and competence, issued by a recognized maritime training authority.

Saltie:

A Great Lakes term for an ocean-going vessel that also navigates inland waters.

Sampson Post:

A strong vertical post that supports the windlass and the base of the bowsprit on a ship’s deck.

SAR (Search and Rescue):

Coordinated operations to locate and assist vessels or people in distress at sea.

SART (Search and Rescue Transponder):

An electronic beacon that helps rescuers pinpoint a vessel’s location by responding to radar signals.

Scandalize:

To reduce a sail’s area quickly without reefing, usually by slackening tension and raising the boom.

Scantling:

The standard dimensions for structural parts of a ship, ensuring strength and uniformity in construction.

Scud:

Low, fast-moving clouds that often signal squally or stormy weather.

Scudding:

When a ship is driven rapidly before a gale or strong wind, often under bare poles.

Scuppers: Deck openings that let rain or seawater drain off safely, preventing pooling.

Scuttle: A small hatch or opening in a ship’s deck or hull; also, the deliberate act of sinking a ship.

Scuttlebutt: Originally a cask of drinking water aboard ship; now, naval slang for gossip or rumor.

Sea Anchor: A drag device deployed overboard to stabilize a vessel in heavy seas and prevent drifting broadside.

Sea Chest: An opening in a ship’s hull used to take in seawater for cooling, ballast, or firefighting systems.

Seacock: A valve that controls the flow of water through the hull, essential for safety and maintenance.

Seafarer: A person who makes their living working aboard ships—a mariner or sailor.

Seaman: A member of a ship’s crew, typically of lower rank but skilled in seamanship.

Seaworthy: Describes a vessel fit, equipped, and safe for sea navigation.

Securité: A radio call used to broadcast important safety information, less urgent than distress calls.

Seelonce: A command for maintaining radio silence during emergencies to ensure clear communication.

Self-Unloader: A Great Lakes vessel fitted with onboard conveyors to discharge cargo without dockside equipment.

Sennet Whip: A braided rope whip once used aboard ships for minor discipline.

Shackle: A metal link with a removable pin, used to connect chains, ropes, or fittings securely.

Sheave: A grooved wheel inside a block or pulley over which rope runs to reduce friction.

Sheer: The upward curve of a ship’s deck line when viewed from the side, giving shape and strength.

Sheet: A rope attached to the lower corner of a sail, controlling its angle and tension relative to the wind.

Ship: A large seagoing vessel capable of deep-water navigation; traditionally a three-masted, square-rigged craft.

Ship’s Bell: A bell used aboard ship to mark time, signal watches, and sound alarms.

Ship’s Company: The complete crew of officers and sailors serving aboard a ship.

Shoal: A shallow area or sandbank that poses a navigational hazard.

Shrouds: Strong lines or wires forming part of the standing rigging, supporting the mast laterally.

Sick Bay: The ship’s medical area where injured or ill crew members receive treatment.

Siren: A loud sound device using compressed air or electricity for signaling or warnings.

Skipper: The captain or master of a vessel, especially on smaller boats.

Skysail: A small sail set above the royal, used only on tall ships in light winds.

Skyscraper: A triangular sail set even higher than the skysail to catch faint breezes.

Slack Tide: The brief period between ebb and flood tides when the water is nearly still.

Sloop: A single-masted sailing vessel with one mainsail and one headsail or jib.

Slop Chest: A store aboard ship selling essential goods like clothes and toiletries to the crew.

Slush: A greasy by-product from boiling or scraping fat, traditionally used to lubricate rigging.

Slush Fund: Money earned from selling slush, often used for the crew’s comfort or unofficial expenses.

Small Bower (Anchor): The smaller of a ship’s two primary bow anchors.

Son of a Gun: Once used for children born aboard ship; now a friendly or teasing term for a lively person.

Sonar: Sound Navigation and Ranging; a system using sound pulses to detect objects underwater.

Sounding: Measuring the water’s depth beneath a vessel using a lead line or echo sounder.

Spar: A general term for poles such as masts, yards, and booms that support sails and rigging.

Spanker: A fore-and-aft sail set on the ship’s rearmost mast to aid steering and balance.

Spanker-Mast: The aft-most mast on vessels like barquentines or schooners, carrying the spanker sail.

Spindrift: Sea spray blown off wave crests by strong winds, common during storms.

Spinnaker: A large, balloon-shaped sail used when sailing downwind to increase speed.

Splice: To join two rope ends by weaving their strands together for strength and durability.

Spotlight: A powerful beam light used for nighttime navigation, signaling, or search operations.

Squall: A sudden, brief, and intense burst of wind, often accompanied by rain or snow.

Stability: The ability of a ship to resist capsizing and return upright after rolling.

Standing Rigging: The fixed rigging that supports a ship’s masts and spars, including shrouds and stays.

Starboard: The right-hand side of a ship when facing forward, marked by a green navigation light.

Starboard Tack: A sailing condition where the wind blows from the starboard side and the boom lies to port.

Station Keeping: Maintaining a steady position relative to another vessel or a fixed point.

Stem: The foremost part of the ship’s bow, rising upward from the keel.

Stern: The rear end of a ship, opposite the bow.

Sternway: The backward motion of a vessel through the water.

Stevedore: A dock worker responsible for loading and unloading cargo.

Stow: To pack and secure gear neatly to prevent shifting at sea.

Stowaway: A person who hides aboard a ship to travel without paying.

Superstructure: The parts of a ship built above the main deck, including the bridge and cabins.

Surge: A quick forward movement of a vessel due to wave force or engine thrust.

Swab: A mop used to clean decks; also, slang for a sailor.

Swamp: When a vessel fills with water but remains afloat rather than sinking.

Swell: Long, rolling waves generated by distant storms, moving independently of local winds.

Swim Platform: A flat extension at the stern near the waterline, used for swimming or boarding.

Tabernacle: A hinged mast step that lets a mast be lowered easily for bridge passage or maintenance.

Tack (noun): The lower front corner of a sail where it’s secured to the deck or boom.

Tack (verb): To steer the boat’s bow through the wind, changing direction from one tack to the other.

Tacking: Sailing close to the wind on alternating courses, repeatedly turning the bow through the wind.

Taffrail: The railing around a ship’s stern, often decorative on older vessels.

Tailshaft: The metal shaft that connects a ship’s propeller to the engine, transmitting power for propulsion.

Taking the Wind Out of His Sails: Sailing in a way that blocks the wind from another vessel’s sails, slowing it down.

Tally: The act of hauling the sheets aft toward the stern to trim the sails.

Tang: A metal fitting used to attach rigging to a mast or spar.

Tank Top: The inner bottom plating of a ship, forming the top surface of the double bottom structure.

Tarpaulin: A durable, weatherproof covering made of tar-coated canvas or synthetic material, used to protect gear and cargo.

Teazer: A rope once used as a disciplinary whip aboard ships.

Tender: A small boat used to carry people or supplies between a larger vessel and shore.

Three Sheets to the Wind: A saying for a drunken sailor; originally referred to loose sail sheets letting a ship drift wildly.

Thwart: A crosswise seat in a rowboat where rowers sit.

Tide: The regular rise and fall of sea levels caused by the gravitational pull of the moon and sun.

Tide Tables: Published charts that predict the timing and height of tides at specific locations.

Tidal Stream: The horizontal movement of seawater caused by tidal forces, crucial for navigation and anchoring.

Timoneer: The helmsman or steersman of a ship, particularly in older nautical terms.

Tiller: A handle attached to the rudder, used for steering small boats.

Tillerman: The person responsible for steering a vessel using a tiller.

Toe Rail: A raised strip along the deck’s edge that offers grip and prevents objects from sliding overboard.

Toe the Line/Mark: To stand in formation with toes on a deck seam; also used to mean strict obedience to rules.

Togey: Another name for a rope used for punishment on naval ships.

Topgallant: The mast or sails above the topsails, forming the third tier on a square-rigged ship.

Topmast: The section of the mast above the lower mast, carrying the topsails.

Topping Lift: A rope that supports the boom when the sail is down, preventing it from dropping to the deck.

Topsail: The sail set above the lowest sail on a mast; on fore-and-aft rigs, it’s set above the mainsail.

Topsides: The outer hull of a vessel above the waterline; also refers to the ship’s upperworks.

Touch and Go: When a vessel’s keel lightly grazes the seabed but continues moving without grounding.

Towing: The act of pulling another vessel using ropes, hawsers, or towlines.

Track: (1) The actual course a vessel travels over the water. (2) A metal or plastic fitting on a mast or boom that holds a sail slide. (3) A fixed path for a traveller system that adjusts sail trim.

TrackLink: A digital GPS tracking app used in sailing education for logging student voyages.

Traffic Separation Scheme: Official sea lanes separating opposing traffic to reduce collision risk in busy waters.

Trapeze: A wire and harness setup allowing sailors to lean far out of small boats to counterbalance heel.

Transom: The flat surface at a vessel’s stern; the structural end forming the back of the hull.

Travellers: Sliding fittings on a bar or line used to adjust sail trim, especially for the mainsheet.

Trim: (1) Adjusting sails for best speed and efficiency. (2) Balancing the vessel’s weight fore and aft for proper handling.

Trim Tab: A small adjustable surface on a rudder or plane that helps steady steering and reduce effort.

Trimaran: A three-hulled vessel with one main hull and two smaller outriggers for extra stability and speed.

Trip Line: A rope attached to an anchor’s crown to help free it if it becomes stuck on the seabed.

True Wind: The actual direction and speed of the wind, felt when stationary—not affected by the vessel’s motion.

Truck: A wooden cap at a mast’s top, often drilled for flag halyards or signal lines.

Trunnel: A wooden peg or dowel used in traditional shipbuilding to fasten timbers together, also called a treenail.

Tsunami: A powerful, long sea wave triggered by underwater disturbances such as earthquakes or volcanic eruptions.

Turnbuckle: A metal device used to adjust rigging tension by rotating a threaded center body.

Turn To: A command for the crew to begin or resume work aboard ship.

Twin Screw: A vessel fitted with two propellers, improving maneuverability and backup propulsion.

Turtling: A complete capsize where a sailboat overturns with its mast pointing downward like a turtle’s shell.

Unbend: To detach a sail from its yard, boom, or stay after use, preparing it for storage or maintenance.

Under the Weather: Originally referred to sailors working on the windward side of the ship, exposed to harsh weather; now used for feeling unwell.

Under Way: Describes a vessel in motion or navigating freely—not anchored, moored, or aground. Specifically, a ship is underway when it’s not attached to the shore or resting on the seabed.

Underwater Hull (or Underwater Ship): The portion of a vessel’s hull that remains submerged below the waterline, visible only when in drydock.

Unfurl: To open and spread a sail so that it catches the wind and begins drawing power.

Unship: To remove equipment or fittings from their usual place aboard, such as unshipping oars or spars.

Up Haul: A rope or line used to lift equipment vertically—commonly used to raise a spinnaker pole on sailing vessels.

Upper Deck: The highest continuous deck running the full length of a ship, typically exposed to the open air.

Upper-yardmen: Sailors chosen for advanced seamanship training or leadership roles, often marked for promotion or specialized duties.

V-berth: A sleeping area located at the bow of a boat, shaped like the letter “V” to fit the hull’s contour.

Vanishing Angle: The critical heel angle beyond which a vessel cannot recover its upright position and is at risk of capsizing.

Vang (or Kicking Strap): A rope or mechanical system used to control the boom’s vertical movement, keeping the sail flat and efficient.

Veer: (1) A clockwise change in wind direction. (2) To gradually pay out or ease a rope, cable, or anchor chain.

Vessel: A general term describing any craft designed for water transport, from small boats to large ships.

VHF (Very High Frequency): The range of radio frequencies used for marine communication, typically between 156 and 174 MHz.

Visor: The hinged bow door on a roll-on/roll-off (RoRo) vessel, allowing vehicles to embark and disembark.

VMG (Velocity Made Good): A measure of a vessel’s actual progress toward its destination, accounting for wind and current effects.

Voyage: A journey or passage made by sea from one port or harbor to another.

Wales: Heavy, longitudinal planks running along the outer hull of a ship, strengthening its structure and protecting it from impact.

Wake: The turbulent trail of water left behind by a moving vessel, often used to track a ship’s speed or path.

Wardroom: The living and dining quarters reserved for commissioned officers aboard a naval vessel. Watch: A fixed period during which a portion of the crew is assigned duty, traditionally marked by the striking of the ship’s bell.

Watercraft: A general term encompassing all types of vessels designed for travel or work on water.

Waterline: The visible line where a vessel’s hull meets the surface of the water when afloat.

Watertight: Designed or sealed to prevent water from entering; critical to a ship’s safety and buoyancy.

Way: The movement of a vessel through the water; a ship “making way” is one that is in motion.

Weather Deck: The exposed deck of a ship, typically the uppermost one, open to the elements.

Weather Gage: A superior position upwind of another vessel, offering tactical control in sailing or battle.

Weather Helm: The natural tendency of a sailboat to turn into the wind, requiring counter-steering to maintain course.

Weather Side: The side of a vessel that faces and receives the force of the wind.

Weatherly: Describes a vessel capable of sailing efficiently and closely into the wind.

Weigh Anchor: To lift and secure the anchor in preparation for getting under way.

Wells: Compartments or recesses in the ship’s hold, used for housing pumps or containing liquids.

Wheelhouse: The enclosed area where the ship’s wheel and navigational controls are located; also called the pilothouse or bridge.

Wheel: The primary steering mechanism of a ship, connected to the rudder by cables or hydraulics.

Whisker Pole: A light spar used to hold out a headsail when sailing downwind for better wind capture.

White Horses: White-tipped waves created by strong winds, often signaling rough sea conditions.

Wide Berth: Sufficient space left between vessels or objects to allow safe maneuvering; also means keeping one’s distance.

Wiggle Room: Informal nautical slang for extra room or flexibility in handling or navigation.

WGS84 (World Geodetic System 1984): The global reference system used in GPS and modern charting.

Winch: A rotating drum device used to pull in or adjust tension on ropes, cables, or sails.

Windage: The effect of wind resistance on a vessel’s exposed surfaces, such as masts, rigging, and hull.

Windbound: Unable to depart or make progress due to unfavorable wind conditions.

Windlass: A mechanical device used to raise anchors or heavy loads by winding a chain or rope, usually mounted horizontally.

Windward: The direction from which the wind blows; opposite of leeward.

Wavelength: The distance between two successive wave crests, describing both sea and radio waves.

X-Band: A radar frequency range between 7.0 and 11.2 gigahertz, widely used in marine radar systems for precise navigation and collision avoidance due to its high resolution.

Xebec: A small, swift Mediterranean sailing vessel with three masts, known for its speed and maneuverability, commonly used from the 16th to 19th centuries for trade and privateering.

XTE (Cross Track Error): The measured distance a vessel has drifted off its planned course between two waypoints; a crucial navigation indicator for maintaining the correct route.

Yacht: A vessel designed primarily for leisure, sport, or luxury cruising, ranging from small sailboats to large motor-powered ships.

Yankee: A high-cut jib set forward of the foremast, often used with a staysail to enhance performance in moderate to strong winds.

Yard: A horizontal spar mounted across a mast from which square sails are hung on traditional sailing ships.

Yardarm: The outermost end of a yard; historically used as a reference point for time and direction, as in “the sun is over the yardarm.”

Yarr: A hearty exclamation of agreement or acknowledgment among sailors, often popularized in nautical folklore as “Arrr.”

Yaw: The side-to-side rotation of a vessel’s bow about its vertical axis, often caused by wind or wave action.

Yawl: A two-masted sailing vessel with a smaller mizzen mast positioned aft of the rudder post, known for balance and easy handling.

Zephyr: A soft and gentle breeze, often described as the kind of light wind sailors welcome for calm and steady sailing.

Zincs: Sacrificial metal anodes, usually made of zinc, attached to a boat’s hull or propeller to prevent galvanic corrosion by corroding in place of vital metal components.

Zulu: A 19th-century Scottish fishing vessel noted for its straight stem, sharply raked stern, and excellent seaworthiness in coastal waters.