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 piston faces have small, crescent-shaped reliefs into which the valves extend near the top dead center.

From The Wall Street Journal • Jan. 23, 2026

Young explains that they have fewer moving parts than traditional piston engines, making them easier to maintain, yet deliver surprising power for their relatively compact, lightweight size.

From Los Angeles Times • Apr. 29, 2025

It is aimed at existing pilots who want to transition away from diesel piston engines.

From BBC • Mar. 31, 2025

Many past attempts have featured metal rods inserted into lava, pushed by hand or by spring-loaded piston, or even fired into the lava like a spear, to estimate the viscosity of the flow.

From Science Daily • Jun. 4, 2024

The water turned to steam, drove out the air and forced the piston to the top of the cylinder, where a spring engaged a bolt.

From "The Invention of Science" by David Wootton

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