valve

noun Etymology: Latin valva; akin to Latin volvere to roll — more at voluble Date: 14th century 1. archaic a leaf of a folding or double door 2. [New Latin valva, from Latin] a bodily structure (as the mitral valve) that closes temporarily a passage or orifice or permits movement of fluid in one direction only 3. a. any of numerous mechanical devices by which the flow of liquid, gas, or loose material in bulk may be started, stopped, or regulated by a movable part that opens, shuts, or partially obstructs one or more ports or passageways; also the movable part of such a device b. a device in a brass instrument for quickly channeling air flow through an added length of tube in order to change the fundamental tone by some definite interval c. chiefly British electron tube 4. [New Latin valva, from Latin] one of the distinct usually hinged and movable pieces of which the shell of some shell-bearing animals (as lamellibranch mollusks, brachiopods, and barnacles) consists 5. [New Latin valva, from Latin] a. one of the segments or pieces into which a dehiscing capsule or legume separates b. the portion of various anthers (as of the barberry) resembling a lid c. one of the two encasing membranes of a diatom • valved adjective • valveless adjective