valve

The definition of a valve is a device that opens or closes to let things through or to prevent passage.

(noun)

The part of your heart that opens and closes to let blood enter or to prevent blood from entering is an example of a valve.

See valve in Webster's New World College Dictionary

noun

Archaic either of the halves of a double door or any of the leaves of a folding door
a gate regulating the flow of water in a sluice, channel, etc.
Anat. a membranous fold or structure which permits body fluids to flow in one direction only, or opens and closes a tube, chamber, etc.
Bot.
1. any of the segments into which a pod or capsule separates when it bursts open
2. a lidlike part in some anthers, through which pollen is discharged
3. either of the boxlike halves forming the cell walls of a diatom
Electronics
1. a device, esp. a rectifier, that allows current to flow in only one direction
2. Brit. electron tube
Mech.
1. any device in a pipe or tube that permits a flow in one direction only, or regulates the flow of whatever is in the pipe, by means of a flap, lid, plug, etc. acting to open or block passage
2. the flap, lid, plug, etc.
Music a device in certain brass instruments, as the trumpet, that opens (or closes) an auxiliary to the main tube, lengthening (or shortening) the air column and lowering (or raising) the pitch
Zool.
1. each separate part making up the shell of a mollusk, barnacle, etc.
2. any of the parts forming the sheath of an ovipositor in certain insects

Origin: ME, a door leaf < L valva, leaf of a folding door, akin to volvere, to roll: see walk; valvesenses , , < ModL valva < L

transitive verb, intransitive verb valved, valving

Related Forms:

See valve in American Heritage Dictionary 4

noun

Anatomy A 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.
a. Any 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.
b. The movable control element of such a device.
c. 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
a. One of the paired, hinged shells of certain mollusks and of brachiopods.
b. One of the two silicified halves of the cell wall of a diatom.
c. The entire, one-piece shell of a snail and certain other mollusks.
Botany
a. One of the sections into which the wall of a seedpod or other dehiscent fruit splits.
b. A lidlike covering of an anther.
Chiefly British An electron tube or a vacuum tube.
Archaic Either half of a double or folding door.