noun

1. a thick, circular glass in a roof, ship's deck, etc., for admitting light
2. any circular opening for light or air
3. 1. the circular central mark of a target
   2. a shot that hits this
   3. a direct hit
   4. the exact achievement of a goal aimed at
4. 1. a convex lens for concentrating light
   2. a lantern with such a lens
5. a hard, round candy

Etymology: as in Fr oeil de boeuf, Dan koöie, cow eye, Sw oxoga, ox eye, all applied to small, round windows