Bosun is a nautical term referring to a BOATSWAIN, or a sailor in charge of the maintenance and operation of a ship. The term is derived from the Old English word 'batswegen, ' which means 'boat servant.' The term 'bosun' is also used to refer to a petty officer in the Royal Navy. The crossword solutions for the term 'bosun' are 'BOATSWAIN' (9 letters), 'smee' (4 letters), and 'AYE' (3 letters). 'BOATSWAIN' is the most common term used to refer to a bosun, while 'smee' is an archaic term that is still occasionally used. 'AYE' is a naval term used to signify agreement or understanding.