valve /vælv/ BrE AmE noun [countable]
[ Date: 1400-1500 ; Language: Latin ; Origin: valva 'part of a door' ]
1 . a part of a tube or pipe that opens and shuts like a door to control the flow of liquid, gas, air etc passing through it:
heart valves
2 .
the part on a ↑ trumpet or similar musical instrument that you press to change the sound of the note
3 . British English a closed glass tube used to control the flow of electricity in old radios, televisions etc SYN vacuum tube American English