A boatswain, bo's'n, bos'n, or bosun is an unlicensed member of the deck department of a merchant ship. The boatswain supervises the other unlicensed members of the ship's deck department, and typically is not a watchstander, except on vessels with small crews. Other duties vary depending on the type of ship, her crewing, and other factors.
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boatswain A petty officer on a ship, responsible for the ship's equipment and for controlling the work of the crew.