The term NAV. DESIGNATION refers to the job of an Ensign (ENS) in the United States Navy. An Ensign is a commissioned officer who is responsible for the navigation of a ship or aircraft, as well as the supervision of its crew. They are also responsible for the safety and security of the vessel or aircraft, and for ensuring that all regulations and procedures are followed. Ensigns are typically the lowest-ranking officers in the Navy, but they are still highly respected and valued members of the team.