The movable control element of such a device.
Music A device in a brass wind instrument that permits change in pitch by a rapid varying of the air column in a tube.
Biology One of the paired, hinged shells of certain mollusks and of brachiopods.
Biology One of the two silicified halves of the cell wall of a diatom.
Biology The entire, one-piece shell of a snail and certain other mollusks.
Botany One of the sections into which the wall of a seedpod or other dehiscent fruit splits.
Botany A lidlike covering of an anther.
Chiefly British An electron tube or a vacuum tube.
Archaic Either half of a double or folding door.
To provide with a valve.
To control by means of a valve.