valveless

noun

1. Archaic either of the halves of a double door or any of the leaves of a folding door
2. a gate regulating the flow of water in a sluice, channel, etc.
3. Anat. a membranous fold or structure which permits body fluids to flow in one direction only, or opens and closes a tube, chamber, etc.
4. 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
5. Electronics
   1. a device, esp. a rectifier, that allows current to flow in only one direction
   2. Brit. electron tube
6. 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.
7. 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
8. 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

transitive verb, intransitive verb valved, valving

1. to fit with or make use of a valve or valves
2. to regulate the flow of (a fluid) by means of a valve or valves