Pis'ton, n.

noun

n. [Fr. & Sp. piston, It. pistone, from Lat. pinsere, pistum, to pound, to stamp. See PISTIL.] A short cylinder of metal or other solid substance, which fits exactly the cavity of a pump or barrel, and works up and down in it alternately. It is used in pumps and other engines or machines, for various purposes.

A cutaway illustration of a tall cylindrical mechanical device with a vertical rod, a side pipe, and internal components.