Real Dictionary

tappet in American English
a sliding rod in an engine or machine moved by intermittent contact with a cam and used to move another part, as a valve
noun: a sliding rod, intermittently struck by a cam, for moving another part, as a valve

tappet in Automotive Engineering
noun: A tappet is the part of an engine gear train that converts cam lift into linear reciprocating (= up and down) movement which it transmits to the valve.

tappet in British English
noun: a mechanical part that reciprocates to receive or transmit intermittent motion, esp the part of an internal-combustion engine that transmits motion from the camshaft to the push rods or valves

tappet in Mechanical Engineering
noun: A tappet is a part that transfers motion from one machine part to another, especially the part of an internal-combustion engine that transmits motion from the camshaft to the push rods or valves.