piston

• POS: Noun
• HYPHEN: Pis=ton

CIDE DICTIONARY

piston, n. [F. piston; cf. It. pistone piston, also pestone a large pestle; all fr. L. pinsere, pistum, to pound, to stamp. See Pestle, Pistil.].

 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.  [1913 Webster]

Piston head (Steam Eng.), that part of a piston which is made fast to the piston rod. -- Piston rod, a rod by which a piston is moved, or by which it communicates motion. -- Piston valve (Steam Eng.), a slide valve, consisting of a piston, or connected pistons, working in a cylindrical case which is provided with ports that are traversed by the valve.

OXFORD DICTIONARY

piston, n.
1 a disc or short cylinder fitting closely within a tube in which it moves up and down against a liquid or gas, used in an internal-combustion engine to impart motion, or in a pump to receive motion.
2 a sliding valve in a trumpet etc.

Idiom

piston-ring a ring on a piston sealing the gap between the piston and the cylinder wall. piston-rod a rod or crankshaft attached to a piston to drive a wheel or to impart motion.

Etymology

F f. It. pistone var. of pestone augment. of pestello PESTLE

ROGET THESAURUS

piston

Stopper

N stopper, stopple, plug, cork, bung, spike, spill, stopcock, tap, rammer, ram, ramrod, piston, stop-gap, wadding, stuffing, padding, stopping, dossil, pledget, tompion, tourniquet, cover, valve, vent peg, spigot, slide valve, janitor, doorkeeper, porter, warder, beadle, cerberus, ostiary.