piston

¹ American  

[pis-tuhn] / ˈpɪs tən /

noun

1. 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.

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Piston ² American  

[pis-tuhn] / ˈpɪs tən /

noun

1. Walter, 1894–1976, U.S. composer.

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piston British  

/ 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

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piston Scientific  

/ pĭs′tən /

1. A solid cylinder or disk that fits snugly into a hollow cylinder and moves back and forth under the pressure of a fluid (typically a hot gas formed by combustion, as in many engines), or moves or compresses a fluid, as in a pump or compressor.

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Other Word Forms

• pistonlike adjective
• subpiston noun

Etymology

Origin of piston

First recorded in 1695–1705; from French, from 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, crush”) + -one augmentative suffix

Example Sentences

The temperature contrast drives a piston, which in turn produces mechanical energy.

From Science Daily • Feb. 27, 2026

The compression ratio is a measurement of the cylinder displacement between the two extremes of the piston stroke.

From BBC • Feb. 18, 2026

The higher forces, in turn, would require thicker piston crowns, shortened connecting rods and thicker wrist pins.

From The Wall Street Journal • Feb. 12, 2026

Mexican components often constitute 40% of U.S.-made vehicles, said Ebrard, who cited the example of an auto piston that might cross the border seven times.

From Los Angeles Times • Mar. 27, 2025

The loud noise that Abbey and I had heard was the outboard engine throwing a piston rod, though we didn’t know that at the time.

From "Flush" by Carl Hiaasen

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