boat·swain also bo's'n or bos'n or bo·sun (bō'sən) n. A warrant officer or petty officer in charge of a ship's rigging, anchors, cables, and deck crew.
[Middle English botswein : bot, boat; see boat + swein, mate; see swain.]
bo's'n or bos'n (bō'sən) n. Variants of boatswain.