turret

noun

1. A little tower, frequently a merely ornamental structure at one of the corners of a building or castle.

   “Their Victorian house had three turrets and a large amount of gingerbread trim.”

   “There breathes no being but has some pretence / To that fine instinct called poetic sense; […] / The freeman, casting with unpurchased hand / The vote that shakes the turrets of the land.”

   “Awake! for Morning in the Bowl of Night, Has flung the Stone that puts the Stars to Flight: And Lo! the Hunter of the East has caught The Sultán's Turret in a Noose of light.”

2. (historical)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.
3. A tower-like solder post on a turret board (a circuit board with posts instead of holes).
4. An armoured, rotating gun installation on a fort, ship, aircraft, or armoured fighting vehicle.
5. The elevated central portion of the roof of a passenger car, with sides that are pierced for light and ventilation.
6. A turret head.
7. The central conical ornament atop a spinning roulette wheel.