Turret

From Old English touret, Old French tourette, diminutive of tour a tower, Latin turris. See tower

(plural turrets)

(architecture) a little tower, frequently a merely ornamental structure at one of the corners of a building or castle
(historical, military) a siege tower; a movable building, of a square form, consisting of ten or even twenty stories and sometimes one hundred and twenty cubits high, usually moved on wheels, and employed in approaching a fortified place, for carrying soldiers, engines, ladders, casting bridges, and other necessaries
(military) an armoured, rotating gun installation, on a fort, ship, aircraft, or armoured fighting vehicle
(railroads) the elevated central portion of the roof of a passenger car. Its sides are pierced for light and ventilation
(electronics) a tower-like solder post on a turret board (a circuit board with posts instead of holes)