Tappet

n.

1.

(Mach.) A lever or projection moved by some other piece, as a cam, or intended to tap or touch something else, with a view to produce change or regulate motion. Tappet motion a valve motion worked by tappets from a reciprocating part, without an eccentric or cam, - used in steam pumps, etc.

Noun

1.

tappet - a lever that is moved in order to tap something else

lever