Noun
(colloquial) One whose function in an organization is to defend it from attackers, for example, in public relations or public affairs.
One who operates the gun or guns in the tail of a military aircraft, usually a bomber.
Source: en.wiktionary.orgConnick began his acting career as a tail gunner in the World War II film Memphis Belle (1990). Source: Internet
In its final version, the G-12, an interim armament modification, eliminated the lower Bendix turret and added a starboard dual gun pack, waist guns and a canopy for the tail gunner to improve the view when firing the single tail gun. Source: Internet