n 1  :  a structure esp. in a vein or lymphatic that closes temporarily a passage or orifice or permits movement of fluid in one direction only  2  :  any of various mechanical devices by which the flow of liquid (as blood) 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 .
 
 
 
Similar sounding terms:  FeLV  flava  val·va  vul·va 
 
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