turret

Etymology

From Middle English touret, from Old French torete (French tourette), diminutive of tour (“tower”), from Latin turris. See tower.

noun

1. (architecture) A little tower, frequently a merely ornamental structure at one of the corners of a building or castle.
   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. 1836, Oliver Wendell Holmes, Sr., “Poetry: A Metrical Essay”, republished in The Poems of Oliver Wendell Holmes, Boston, Mass.: Ticknor and Fields, 1862, OCLC 5091562, pages 7–8
   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 1859, Edward Fitzgerald, The Rubáiyát of Omar Khayyám: The Astronomer-Poet of Persia, page 1
2. (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.
3. (electronics) A tower-like solder post on a turret board (a circuit board with posts instead of holes).
4. (military) An armoured, rotating gun installation on a fort, ship, aircraft, or armoured fighting vehicle.
5. (rail transport) The elevated central portion of the roof of a passenger car, with sides that are pierced for light and ventilation.