Boom.
1. (Nautical.) a. A spar for extending the foot of a fore-and-aft sail. The boom on which a fore-and-aft sail is stretched is commonly provided with jaws which partially encircle the mast, and are held to it by a half-grommet strung with balls of hard wood to avoid friction. b. A spar rigged out from a yard to extend the foot of a studding-sail. The fore and main lower yards, and the fore and main topsail yards have studding-sail booms. Each is secured by boom-irons on its yard, and is named from the studding-sail whose foot it stretches. The heads of the studding-sails are bent to studding-sail yards which are slung from the studdingsail booms and the fore and main top-gallant yardarms. The stays of these booms are called guys. The ring-tail boom is rigged out like a studdingsail boom at the end of the spanker-boom. c. The booms; the space on the spar-deck between the fore and main masts, where the boats and spare spars are stowed.
2. (Marine Fortification.) A chain or line of connected spars stretched across a river or channel to obstruct navigation, or detain a vessel under the fire of a fort.
3. (Lumbering.) A spar or line of floating timbers stretched across a river, or inclosing an area of water, to keep saw-logs from floating down the stream.
