A Ship's Petty Officer is a rank in the Navy, Coast Guard, and Merchant Marine. The two most common terms for this position are BOSUN (5 letters) and Bosn (4 letters). A BOSUN is responsible for supervising the crew, maintaining the ship's equipment, and ensuring the safety of the vessel. A Bosn is a more senior version of the BOSUN, and is responsible for all of the same duties, as well as providing leadership and guidance to the crew.