valve
nounAny of various devices that regulate the flow of gases, liquids, or loose materials through piping or through apertures by opening, closing, or obstructing ports or passageways.
nounThe movable control element of such a device.
nounA device in a brass wind instrument that can be opened or closed to change the pitch by altering the length of the air column in the tube.
nounA membranous structure in a hollow organ or passage, as in an artery or vein, that folds or closes to prevent the return flow of the body fluid passing through it.
nounA piece of shell covering or enclosing certain mollusks or other invertebrates, especially the single one of a univalve mollusk or one of the paired hinged ones of a bivalve mollusk or brachiopod.
nounOne of the two siliceous halves of the cell wall of a diatom.
nounOne of the pieces into which a plant part splits at maturity, especially a segment of a fruit capsule or of certain anthers.
nounAn electron tube or a vacuum tube.