piston

/ˈpɪstn/

/ˈpɪstən/

Other forms: pistons

A piston is a part of an engine that moves up and down inside a cylinder. Pistons help propel a vehicle by pushing fuel and air into a small space, where a spark plug can ignite and get things moving.

A piston is a small but vital element in a complicated machine. Lawnmowers and motorcycles can have one piston or as many as 12. Most cars have four, six, or eight pistons. The exact way pistons work depends on the specific type of engine, but they're always essential. The word itself comes from the piston's repetitive movement — it shares a root meaning of "to pound" with pestle, the tool used for pounding and grinding spices.

Definitions of piston

1. noun

   mechanical device that has a plunging or thrusting motion
   synonyms: plunger

   type of:

   mechanical device

   mechanism consisting of a device that works on mechanical principles