valveless

/ˈvælvləs/
adjective
  1. Having no valve or valves; lacking a device to control the flow of liquid, gas, or sound.
    • The valveless design of the old engine made it simpler but less efficient.
    • Some early brass instruments were valveless, so players could only produce a limited set of notes.
    • A valveless pump relies on the movement of the fluid itself to prevent backflow.
Antonyms
What does "valveless" mean? | whatsthatwordmean | whatsthatwordmean