Noah Webster's New International Dictionary of the English Language
1. (n.) A little tower, frequently a merely ornamental structure at one of the angles of a larger structure.
2. (n.) 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. (n.) A revolving tower constructed of thick iron plates, within which cannon are mounted. Turrets are used on vessels of war and on land.
4. (n.) The elevated central portion of the roof of a passenger car. Its sides are pierced for light and ventilation.