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[pis-tuh n] /ˈpɪs tən/
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.
a pumplike valve used to change the pitch in a cornet or the like.
Origin of piston
1695-1705; < French < 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
Related forms
pistonlike, adjective
subpiston, noun


[pis-tuh n] /ˈpɪs tən/
Walter, 1894–1976, U.S. composer. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for piston
Historical Examples
  • He employed a cylinder 12 centimeters in diameter fitted with a piston.

  • If steam is forced into the cylinder the piston will be forced to the opposite end of the cylinder.

    Boys' Book of Model Boats Raymond Francis Yates
  • It will be seen that a groove, M, is cut around the piston near the top.

    Boys' Book of Model Boats Raymond Francis Yates
  • The momentum of the flywheel A pushes the piston upward, closing these holes.

    Boys' Book of Model Boats Raymond Francis Yates
  • This cylinder block is soldered to the piston as shown in Fig. 56.

    Boys' Book of Model Boats Raymond Francis Yates
  • A flywheel keeps an engine going between the strokes of the piston.

    Common Science Carleton W. Washburne
  • The diameter of piston is four inches and the length of stroke is six inches.

    Rural Hygiene Henry N. Ogden
  • One here is shown with the piston detached, and also ready for use.

    Home Life in Colonial Days Alice Morse Earle
  • He depressed the piston, pumping the antidote into her bloodstream.

    Vigorish Gordon Randall Garrett
  • It has been used in piston rods and crank shafts for American airplanes.

British Dictionary definitions for piston


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
Word Origin
C18: via French from Old Italian pistone, from pistare to pound, grind, from Latin pinsere to crush, beat
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for piston

1704, from French piston, from Middle French piston "large pestle," from Old Italian pistone "a piston," variant of pestone "a pestle," from pestare "to pound," from Late Latin pistare, frequentative of Latin pinsere (past participle pistus) "to pound" (see pestle). As a verb from 1930.

Online Etymology Dictionary, © 2010 Douglas Harper
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piston in Science

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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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