noun
A device that controls the flow of a gas or fluid through a space, such as a pipe, manifold, or plenum.
(anatomy) One or more membranous partitions, flaps, or folds, which permit the passage of the contents of a vessel or cavity in one direction, but stop or control the flow in the opposite direction.
One of the leaves of a folding door or of a window sash.
(chiefly British) A vacuum tube.
(botany) One of the pieces into which certain fruits naturally separate when they dehisce.
(botany) A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, such as in the barberry.
(biology) One of the pieces or divisions of bivalve or multivalve shells.
(biology) One of the two similar portions of the shell of a diatom.
verb
(transitive) To control (flow) by means of a valve.