piston
//ˈpɪstən//
Noun
pistonSingular
pistonsPlural
1
A cylindrical component that moves up and down inside a cylinder in an engine or pump, transferring force to or from a fluid.
The mechanic replaced the worn piston in the car engine.
2
A sliding valve in a brass musical instrument that changes the pitch by altering the length of the air column.
The trumpet player pressed the pistons to change the notes.