noun A device that controls the flow of a gas or fluid through a space, such as a pipe, manifold, or plenum.
open the valve
noun Such a device that admits fuel and air into the cylinder of an internal combustion engine, or one that allows combustion gases to exit.
In nearly all internal combustion engines, the valves are of the poppet type.
noun 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.
the ileocecal valve
noun One of the leaves of a folding door or of a window sash.
noun A vacuum tube.
noun One of the pieces into which certain fruits naturally separate when they dehisce.
noun A small portion of certain anthers, which opens like a trapdoor to allow the pollen to escape, such as in the barberry.
noun One of the pieces or divisions of bivalve or multivalve shells.