piston

UK: /ˈpɪst^ən/ US: /ˈpɪstən/ ,(pis′tən)

WordReference Random House Learner's Dictionary of American English © 2025

pis•ton /ˈpɪstən/   n. [countable]

1. Mechanical Engineering a disk or solid, pipe-shaped piece moving within a longer tube and putting pressure on, or receiving pressure from, a fluid or gas:
   When the gas mixture explodes it forces the piston down, and this motion is transferred to the car's wheels.
2. a pumplike valve used to change the pitch in a cornet, trumpet, or the like.

WordReference Random House Unabridged Dictionary of American English © 2025

pis•ton  (pis′tən), n. 

1. Mechanical Engineering a disk or cylindrical part tightly fitting and moving within a cylinder, either to compress or move a fluid collected in the cylinder, as air or water, or to transform energy imparted by a fluid entering or expanding inside the cylinder, as compressed air, explosive gases, or steam, into a rectilinear motion usually transformed into rotary motion by means of a connecting rod.
2. a pumplike valve used to change the pitch in a cornet or the like.

• Italian pistone piston, a learned alteration of pestone large pestle, equivalent. to pest(are) to pound (variant of Medieval Latin pistare, derivative of Latin pīstus past participle of pīnsere to pound) + -one augmentative suffix
• French
• 1695–1705

pis′ton•like′, adj. 

Pis•ton  (pis′tən), n. 

1. Biographical Walter, 1894–1976, U.S. composer.

Collins Concise English Dictionary © HarperCollins Publishers::

piston / ˈpɪstən/ noun

1. a disc or cylindrical part that slides to and fro in a hollow cylinder. In an internal-combustion engine it is forced to move by the expanding gases in the cylinder head and is attached by a pivoted connecting rod to a crankshaft or flywheel, thus converting reciprocating motion into rotation

Etymology: 18th Century: via French from Old Italian pistone, from pistare to pound, grind, from Latin pinsere to crush, beat