unit of United States Power Squadrons Sail and Power Boating


Nautical Glossary



Adrift - Unattached to shore or bottom, floating out of control.

Aft, After - At, near, or toward the stem.

Aground - Touching or stuck on the bottom.

Ahead - In front of the boat, forward; opposite of astern.

Aids to Navigation - harted objects available to assist in determination of position or safe course or to warn of danger (e.g., buoys, beacons, fog signals, lights, radio beacons, range marks). Also, any electronic device used for navigation.

Amidship - In or near the middle of the boat.

Anchor - Device used to secure boat to bottom of body of water.

Astern - In back of or behind the boat; backward, opposite of ahead.

Auxiliary - The engine of a sailboat; a sailboat with an auxiliary engine.


Back - To cause to move backwards. Also, change in direction of the wind in a counterclockwise direction in the northern hemisphere, and a clockwise direction in the southern hemisphere.

Backstay - Part of standing rigging, usually cable, that supports a mast from aft.

Batten - Stiffening strip placed in leech of sail. Also a wooden strip fastened over a seam to stop leakage.

Beacon - Anything that serves as a signal or indication for guidance or warning. A fixed (non-floating) aid to navigation.

Beam - Maximum width of a boat. Also, a horizontal athwartship support for the deck.

Berth - A bed on a boat. Also, a place where a boat may be moored.

Bilge - Lowest part of a boat's interior.

Boat Hook - A pole with a hook on one end used to retrieve lines or other items. Also used to fend-off.

Boom - Spar used to extend and control foot of fore-and-aft sail.

Bow - Forward end of a boat.

Bow Line - A line used at the bow of a vessel.

Bridle - A length of line or wire rope with both ends secure (or a secured loop) to the middle of which another line is attached.

Broach - Turn a boat broadside to wind or waves, subjecting it to possible capsizing.

Buoy - Anchored floating device used as an aid to navigation. May carry a light, horn, whistle, bell, gong, or combination for identification. Also may be used to mark a mooring (i.e., anchor buoy).

Buoyancy - The upward force exerted by a fluid on a body or object in that fluid. The upward force that keeps a boat floating.


Cabin - The enclosed or decked-over living space of a boat.

Capsize - To turn over, upset.

Cast Off - To let go a line; to set loose, unfasten; to undo all mooring lines in preparation for departure.

Catamaran - Boat with twin, narrow hulls connected by a deck or crossbeams, resulting in a wide beam and good stability.

Centerboard - Pivoted board that can be lowered through a slot in the keel to reduce leeway.

Chafing Gear - Sacrificial wrapping around lines, rigging, or spars to prevent wear.

Chain Plate - Metal strap on a sailboat, usually secured to the hull or bulkhead or elsewhere, to which a shroud or stay is attached.

Channel - Portion of a waterway that is navigable. May be marked with navigation aids.

Charts - Special maps containing information of use for mariners. Charts show water depth, significant land objects, navigation aids, hazards to navigation.

Chock - Fitting to guide a line or cable. Also, wedge or block to keep an object from moving.

Cleat - Fitting, usually with two projecting horns, to which lines are made fast.

Cleat Hitch - A hitch used to attach a line to a cleat. Looks like a figure-eight, is easily made and released.

Cockpit - Well or sunken space in the deck.

COLREGS - International Regulations for Preventing Collisions at Sea (distributed by the U.S. Coast Guard).

Compass Error - Combined effect of variation and deviation.

Crest - The top of a wave.

Cuddy - A shelter cabin in a small boat.

Current - The horizontal movement of water. Also, the movement of electrons through a conductor.


Daybeacon, Daymark - Unlighted fixed aid to navigation.

Daysailer - Sailboat without amenities, such as a cabin, used for short duration sailing.

Dead Reckoning (DR) - Calculating a boat's position based on its course, speed, and time run from a previous position.

Deck - Nautical equivalent of a floor.

Deck House - A partially enclosed structure erected on the deck.

Dinghy - Small open boat used as a lifeboat or tender.

Displacement - The weight of water displaced by a floating vessel; hence, the weight of the vessel itself.

Dock - Area of water in which a boat rests between two landing piers or wharves.

Draft - Depth of water needed to float a boat. Also, the fullness or "belly" of a sail.

Drift - Movement of a boat due to wind and current; velocity (speed) of current.


Fender - Protective device between a boat and another object.

Fairway - A channel.

Fiberglass - Synthetic material for boat building. A glass fiber impregnated with a polyester or epoxy resin.

Flame Arrestor - A screen-like metal fitting fastened over a carburetor air intake to keep backfire flames from flashing out into an engine compartment where they could ignite gasoline fumes.

Float Plan - An outline plan of a cruise left at one's home port or with friends to provide a description of the boat, list of persons on board, list of safety equipment carried, and, most importantly, where the boat will be cruising and when it is expected to return to home port.

Flybridge (Flying Bridge) - A helm station located atop the cabin of a powerboat.

Fore - Denoting at, near, or towards the bow.

Foredeck - The deck of a boat located near the bow.

Forestay - A stay below and aft of the headstay on a yacht carrying two headsails. Also used as the term for headstay.

Forward - Toward the bow.

Foul - Jammed, entangled; not clear; being hindered or impeded.

Freeboard - Vertical distance from the water surface to the lowest point where unwanted water could come aboard.


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Lt. Michael Hollis, P