A sliding piece which either is moved by, or moves against, fluid pressure. It usually consists of a short cylinder fitting within a cylindrical vessel along which it moves, back and forth. It is used in steam engines to receive motion from the steam, and in pumps to transmit motion to a fluid; also for other purposes.

Pump Module component. Part of the piston/cylinder set.

The head which moves inside the cylinders of a steam locomotive when pressured by steam.

A disk or short cylinder attached centrally to a rod and fitted closely inside a hollow cylinder, within which it can be driven up and down by fluid pressure (in engines).

See ram.

Some larger rockets use a "piston" which pushes the Recovery Device out

Another name for the manual espresso machine. The barista has to operate it himself, by pushing a lever, in order to force the water through the coffee grounds.

A device used for converting hydraulic power to mechanical energy. In hydraulic pumps, the piston is responsible for pushing down and pulling up the ram.