Noun

1. A slatted opening in a wall, door or window.
2. Any of a series of narrow openings framed at their longer edges with slanting, overlapping fins or slats, adjustable for admitting light and air while shutting out rain.
3. A fin or slat framing such an opening.
4. A ventilating turret or lantern, as on the roof of a medieval building.
5. Any of a system of slits, as in the hood of an automobile, for ventilation.