The copilot of an aircraft. / The chief mate of a merchant ship. / The executive officer, second in command of a naval vessel.

(aviation) The flight engineer of an aircraft.

A relief aircrew member, often used on long-distance flights.

(military) second in command of a military unit or ship

A fellow police officer

A person assigned to manage a client's affairs. / In intelligence organisations, a person who manages a network of agents.

plural of customs officer

plural of case officer

A government-established place (building, office, shop, or counter) offering advice on tax affairs.

plural of tax office