A glossary of nautical terms

Each month, we will add nautical terms to this list in alphabetical order. This is a partial glossary of nautical terms; some remain current, while many date from the 17th to 19th centuries.

A to C - D to F - G to I - J to L - M to O

Gaff - 1. Gaff rig: The spar that holds the upper edge of a four-sided fore-and-aft mounted sail. 2. Fishing gaff: A hook on a long pole to haul fish in.
Gaff rigged - A boat rigged with a four-sided fore-and-aft sail with its upper edge supported by a spar or gaff which extends aft from the mast.
Gaff vang - A line rigged to the end of a gaff and used to adjust a gaff sail's trim.
Galleass - 1. An oared warship of the 1500s equipped with a gundeck, larger and equipped with more sails than a galley. 2. A flat-bottom commercial sailing vessel of the North Sea and western Baltic Sea.
Galleon - A large, multi-decked sailing ship used primarily by European states from the 16th to 18th centuries.
Galley - 1. Galley, the kitchen of a ship. 2. Galley, a type of ship propelled by oars used especially in the Mediterranean for warfare, piracy, and trade from the 700s BC to the 1500s AD, with some in use until the early 1800s. 3. A type of oared gunboat built by the United States in the late 18th century, akin to a brigantine but termed "galley" for administrative and funding purposes.
Gam - A meeting of two (or more) whaling ships at sea. The ships each send out a boat to the other, and the two captains meet on one ship, while the two chief mates meet on the other.
Gammon iron - The bow fitting which clamps the bowsprit to the stem.
Gangplank - A movable bridge used in boarding or leaving a ship at a pier; also known as a "brow".
Gangway - An opening in the bulwark of the ship to allow passengers to board or leave the ship.
Garbling - The (illegal) practice of mixing cargo with garbage.
Garboard - The strake closest to the keel (from Dutch gaarboard).
Garboard planks - The planks immediately either side of the keel.
Gash - Any refuse or rubbish which is discarded into a refuse container or dustbin which is known as "gash fanny" (South African Navy).
Gasket - A rope used to secure a sail (particularly the topsail) when stowed.
Gear - A vessels sails and rigging.
General Quarters - See Battle Stations.
Gennaker - A large, lightweight sail used for sailing a fore-and-aft rig down or across the wind, intermediate between a genoa and a spinnaker.
Genoa or genny - A large jib, strongly overlapping the mainmast.
Ghost - To sail slowly when there is apparently no wind.
Gibe - See gybe.
Gig (Captain's gig) A boat on naval ships at the disposal of the ship's captain for his or her use in transportation to other ships or to the shore.
Gin-pole - A pole that is attached perpendicular to the mast, to be used as a lever for raising the mast. Also jin-pole.
Give-way (vessel) - Where two vessels are approaching one another so as to involve a risk of collision, this is the vessel which is directed to keep out of the way of the other.
Glass - A marine barometer. (Older barometers used mercury-filled glass tubes to measure and indicate barometric pressure.)
Global Positioning System - (GPS) A satellite based radionavigation system providing continuous worldwide coverage. It provides navigation, position, and timing information to air, marine, and land users.
Go-fast boat - is a small, fast boat designed with a long narrow platform and a planing hull to enable it to reach high speeds – also called 'a rum-runner', or, more recently, 'a cigarette boat'.
Goat locker - A mess hall reserved for Chief petty officers in the US Navy.
Going about or tacking - Changing from one tack to another by going through the wind (see also gybe).
Gondola - A traditional, flat-bottomed Venetian rowing boat.
Gooseneck - Fitting that attaches the boom to the mast, allowing it to move freely.
Goosewinged - Of a fore-and-aft rigged vessel sailing directly away from the wind, with the sails set on opposite sides of the vessel – for example with the mainsail to port and the jib to starboard, to maximize the amount of canvas exposed to the wind. See also running.
Grapeshot - Small balls of lead fired from a cannon, analogous to shotgun shot but on a larger scale. Similar to canister shot but with larger individual shot. Used to injure personnel and damage rigging more than to cause structural damage.
Grave - To clean a ship's bottom.
Graving dock - A narrow basin, usually made of earthen berms and concrete, closed by gates or by a caisson, into which a vessel may be floated and the water pumped out, leaving the vessel supported on blocks; the classic form of drydock.
Green-to-green - A passage of two vessels moving in the opposite direction on their starboard sides, so called because the green navigation light on one of the vessels faces the green light on the other vessel.
Great circle - The line that follows the shortest distance between two points on the globe.
Gripe - Temporary eye in a line (rope).
Gripie - Cockney (London dialect) name for a barge.
Grog - Watered-down pusser's rum consisting of half a gill with equal part of water, issued to all seamen over twenty. (CPOs and POs were issued with neat rum) From the British Admiral Vernon who, in 1740, ordered the men's ration of rum to be watered down. He was called "Old Grogram" because he often wore a grogram coat, and the watered rum came to be called 'grog'. Often used (illegally) as currency in exchange for favours in quantities prescribed as 'sippers' and 'gulpers'. Additional issues of grog were made on the command 'splice the mainbrace' for celebrations or as a reward for performing especially onerous duties. The RN discontinued the practice of issuing rum in 1970. A sailor might repay a colleague for a favour by giving him part or all of his grog ration, ranging from "sippers" (a small amount) via "gulpers" (a larger quantity) to "grounders" (the entire tot).
Groggy - Drunk from having consumed a lot of grog.
Ground - The bed of the sea.
Grounding - When a ship (while afloat) touches the bed of the sea, or goes "aground".
Growler - A small iceberg or ice floe which is barely visible above the surface of the water.
Guard boat - A boat which makes the rounds of a fleet at anchor to see that due watch is kept at night.
Guard ship - 1. A warship stationed at a port or harbour to act as a guard there. 2. In former times in the British Royal Navy, a ship which received men impressed for naval service, often the flagship of the admiral commanding along the coast. 3. In Soviet and Russian terminology, a guard ship (storozhevoj korabl') is a small, general purpose patrol or escort vessel.
Gun deck - 1. Up through the 19th century, a deck aboard a ship that was primarily used for the mounting of cannon to be fired in broadsides. 2. On smaller vessels (of frigate size or smaller) up through the 19th century, the completely covered level under the upper deck, even though in such smaller ships it carried none of the ship's guns. 3. On marine seismic survey vessels, the lowest deck on the ship, which carries the seismic source arrays, consisting of air guns arranged in clusters. 4. In naval slang, to fabricate or falsify something; in modern usage, meaning especially to falsify documentation in order to avoid doing work or make present conditions seem acceptable without having made a real effort to improve them.
Gunport - The opening in the side of the ship or in a turret through which the gun fires or protrudes.
Gunter - 1. A wire that leads from one point near the end of a gaff to a point near the other end; a block travels along the wire and a halyard is attached to the block, allowing the gaff to be raised to the vertical by a single halyard, though another halyard is required at the gaff jaws to control height. 2. Hoops or parrel beads which secure a gaff loosely to a mast in a vertical position; a halyard is bent to the gaff jaws to control height.
Gunter rig - A vessel with a gunter-rigged mainsail.
Gunter-rigged - A sail raised by means of a gunter.
Gunwale - Upper edge of the hull. The top timber on the rail round the outer edge of the deck.
Gybe or jibe - To change from one tack to the other away from the wind, with the stern of the vessel turning through the wind. (See also going about and wearing ship.)

Book a Course

Half-breadth plan - In shipbuilding, an elevation of the lines of a ship, viewed from above and divided lengthwise.
Halyard or halliard - Originally, ropes used for hoisting a spar with a sail attached; today, a line used to raise the head of any sail.
Hammock - Canvas sheets, slung from the deckhead in messdecks, in which seamen slept. "Lash up and stow" a piped command to tie up hammocks and stow them (typically) in racks inboard of the ship's side to protect crew from splinters from shot and provide a ready means of preventing flooding caused by damage.
Hand - To furl a sail.
Hand bomber - A ship using coal-fired boilers shoveled in by hand.
Hand over fist - To climb steadily upwards, from the motion of a sailor climbing shrouds on a sailing ship (originally "hand over hand").
Handsomely - With a slow even motion, as when hauling on a line "handsomely".
Handy billy - A loose block and tackle with a hook or tail on each end, which can be used wherever it is needed. Usually made up of one single and one double block.
Hangar deck - An enclosed deck, usually beneath the flight deck, on an aircraft carrier intended for use as a hangar in servicing and storing aircraft.
Hank - A fastener attached to the luff of the headsail that attaches the headsail to the forestay. Typical designs include a bronze or plastic hook with a spring-operated gate, or a strip of cloth webbing with a snap fastener.
Harbour - A harbour or harbor (US), or haven, is a place where ships may shelter from the weather or are stored. Harbours can be man-made or natural.
Harbor of refuge - A place where ships in transit can find shelter from a storm. These are often man-made jetty enclosed areas along a featureless coastline where no nearby natural deep water harbors exist.
Hard - A section of otherwise muddy shoreline suitable for mooring or hauling out.
Harden in - Haul in the sheet and tighten the sails.
Harden up - Turn towards the wind; sail closer to the wind.
Harness cask - A large usually round tub lashed to a vessel's deck and containing dried and salted provisions for daily use.
Harness tub - See "harness cask".
Hardtack - A hard and long-lasting dry biscuit, used as food on long journeys. Also called ship's biscuit.
Hatchway, hatch - A covered opening in a ship's deck through which cargo can be loaded or access made to a lower deck; the cover to the opening is called a hatch.
Haul - 1. To steer (a vessel) closer to the direction of the wind. 2. To shift forward, i.e., more toward the bow of the vessel.
Hauling wind - Pointing the ship towards the direction of the wind; generally not the fastest point of travel on a sailing vessel.
Hawsepipe, hawsehole or hawse - The shaft or hole in the side of a vessel's bow through which the anchor chain passes.
Hawsepiper - An informal term for a merchant ship's officer who began their career as an unlicensed merchant seaman, and so did not attend a traditional maritime academy to earn their officer's licence (see also before the mast).
Hawser - Large rope used for mooring or towing a vessel.
Head - 1. The forwardmost or uppermost portion of the ship. 2. The forwardmost or uppermost portion of any individual part of the ship, e.g., the masthead, the beakhead, the stemhead, etc. 3. The top edge of a sail. 4. The toilet or latrine of a vessel, which in sailing ships projected from the bows and therefore was located in the "head" of the vessel.
Head boat - A fishing boat that takes recreational fishermen out for a fee paid individually by each person (i.e., per head). A head boat differs from a charter boat, which is a fishing boat that a party of fishermen hires for an agreed-upon period.
Head of navigation - The farthest point above the mouth of a river that can be navigated by ships.
Head rail - A curved rail that extends from the figurehead to the bow of a ship.
Head rope - Part of the bolt rope, at the head of a sail, running from the mast to the sprit.
Head sea - A sea where waves are directly opposing the motion of the ship.
Header - A change in the wind direction which forces the helmsman of a close hauled sailboat to steer away from its current course to a less favorable one. This is the opposite of a lift.
Heading - The direction a thing's nose is pointing.
Headsail and Headsails - Any sail flown in front of the most forward mast. Headsails the collective name for all sails afore the mast.
Headstick - The spar laced to the head of the topsail.
Heave - A vessel's transient, vertical, up-and-down motion.
Heave down - Turn a ship on its side (for cleaning). Also known as Careening.
Heaving to - Or Hove to. Stopping a sailing vessel by lashing the helm in opposition to the sails. The vessel will gradually drift to leeward, the speed of the drift depending on the vessel's design.
Heel - 1. The lean caused by the wind's force on the sails of a sailing vessel. 2. The inclination or canting of a vessel to one side or the other from the vertical as she maneuvers, as The ship heeled to port as she turned to starboard. 3. The lowest or last part of something, such as the heel of the mast or the heel of the vessel.
Helm - A ship's steering mechanism; see tiller and ship's wheel. The wheel and/or wheelhouse area. See also wheelhouse. Take the helm, means take over the steering of the vessel.
Helmsman - A person who steers a ship.
Herring buss - A type of seagoing fishing vessel used by Dutch and Flemish herring fishermen from the 15th through the early 19th century.
Highfield lever - A particular type of tentioning lever, usually for running backstays. Their use allows the leeward backstay to be completely slackened so that the boom can be let fully out.
Hitch - A knot used to tie a rope or line to a fixed object. See also bend.
Hog - 1. A fore-and-aft structural member of the hull fitted over the keel to provide a fixing for the garboard planks. 2. A rough flat scrubbing brush for cleaning a ship's bottom under water.
Hogging - When the peak of a wave is amidships, causing the hull to bend so the ends of the keel are lower than the middle. The opposite of sagging. Also refers to a permanent distortion of the hull in the same manner caused, over time, by the bow and stern of a ship being less buoyant than the midships section. During the Age of Sail, shipwrights employed a number of different designs of braces to stiffen ships' hulls against this warping.
Hoist - The height of a fore-and-aft sail as measured next to the mast or stay.
Hold - In earlier use, below the orlop deck, the lower part of the interior of a ship's hull, especially when considered as storage space, as for cargo. In later merchant vessels it extended up through the decks to the underside of the weather deck.
Holiday - A gap in the coverage of newly applied paint, slush, tar or other preservative.
Holystone - A chunk of sandstone used to scrub the decks. The name comes from both the kneeling position sailors adopt to scrub the deck (reminiscent of genuflection for prayer), and the stone itself (which resembled a Bible in shape and size).
Home port - The port at which a vessel is based. Often confused with the ship's port of registry, which is the port listed in the vessel's registration documents and lettered on her stern and which may differ from her home port. In the cruise ship industry, the term "home port" often is mistakenly used to refer to a ship's port of departure.
Homeward bounder - Deep sea expression for a sail repair, done with large herringbone stitches.
Hoop - Wooden or metal hoops used to secure the topsail to the topmast so it can be speedily raised or lowered.
Horn - A sound signal which uses electricity or compressed air to vibrate a disc diaphragm.
Horns - Shaped ends to the chocks where the main horse is bolted.
Horn timber - A fore-and-aft structural member of the hull sloping up and backwards from the keel to support the counter.
Horse - 1. Sand lying mid-channel. 2. Prominent wooden or iron beams lying across the deck of a sailing barge taking the foresheet and mainsheet. 3. Attachment of sheets to deck of vessel (main-sheet horse). 4. (v.) To move or adjust sail by brute hand force rather than using running rigging.
Hounds - Attachments of stays to masts.
Hotel load - The electrical load for all non-propulsion systems on a ship.
Hoy - Barge making regular passages on a fixed route with mixed third-party cargoes. aka Passage barge, goods barge.
Hufflers - Men employed to help the barges crew along tortuous channels or through bridges. See shooting a bridge.
Hulk - 1. A ship, often an old ship or one that has become obsolete or uneconomical to operate, that has had its rigging or internal equipment removed and is incapable of going to sea, but that is afloat and continues to serve a useful function, such as providing living, office, training, storage, or prison space. 2. To convert a ship into such a hulk. 3. Less commonly, a ship that has been launched but not completed. 4. Also less commonly, an abandoned wreck or shell of a ship.
Hull - The shell and framework of the basic flotation-oriented part of a ship.
Hull-down - Of a vessel when only its upper parts are visible over the horizon.
Hull speed - The maximum efficient speed of a displacement-hulled vessel.
Hydrofoil - A boat with wing-like foils mounted on struts below the hull, lifting the hull entirely out of the water at speed and allowing water resistance to be greatly reduced.

Icebreaker - A special-purpose ship or boat designed to move and navigate through ice-covered waters.
Icing - A serious hazard where cold temperatures (below about −10°C) combined with high wind speed (typically force 8 or above on the Beaufort scale) result in spray blown off the sea freezing immediately on contact with the ship.
Idlers - Members of a ship's company not required to serve watches. These were in general specialist tradesmen such as the carpenter and the sailmaker.
In ballast (or "in ballast condition") - Of a vessel: Having only ballast (q.v.) – and no cargo – as a load.
In Irons/In stays - When a sailing vessel has lost its forward momentum while heading into the wind, rendering it unable to steer.
In ordinary - An 18th- and 19th-century term originally used to refer to a naval vessel out of service for repair or maintenance, later coming to mean naval ships in reserve with no more than a caretaker crew.
In-water Survey - A method of surveying the underwater parts of a ship while it is still afloat instead of having to drydock it for examination of these areas as was conventionally done.
In way of - In the vicinity of; in the area of.
Inboard - 1. Situated within a vessel. 2. Situated within a vessel and positioned close (or closer than another item, when contrasted with that item) to her centerline. 3. Situated outside a vessel but nearer to her hull, e.g., The larger boat was tied up alongside the ship inboard of the smaller boat. 4. Nearer the pier or shore, e.g., The tanker and cargo ship were tied up at the pier alongside one another with the tanker inboard of the cargo ship.
Inboard motor - An engine mounted within the hull of a vessel, usually driving a fixed propeller by a shaft protruding through the stern. Generally used on larger vessels. See also sterndrive and outboard motor.
Inglefield clip - A type of clip for attaching a flag to a flag halyard.
Inshore - 1. Near (especially in sight of) or toward the shore. 2. Of a wind, blowing from the sea to the land.
Iron Mike - A slang term for autopilot.
Iron topsail - An auxiliary motor on a schooner.
Iron wind - What sailors call inboard engines.
Ironclad - A steam-propelled warship protected by iron or steel armor plates of the period from 1859 until the 1890s (when the term "ironclad" fell out of use).
Island - The superstructure of an aircraft carrier that extends above the flight deck. A carrier that lacks one is said to be flush-decked.

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