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mainspring

[meyn-spring]
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noun
  1. the principal spring in a mechanism, as in a watch.
  2. the chief motive power; the impelling cause.
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Origin of mainspring

First recorded in 1585–95; main1 + spring
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for mainspring

Historical Examples

  • Perhaps this had originally been the mainspring of the understanding between them.

    Little Dorrit

    Charles Dickens

  • How's she goin' to cock that gun, an' the mainspring fifteen pounds resistance?'

    Faro Nell and Her Friends

    Alfred Henry Lewis

  • That need is the mainspring of life, the key to heaven, and the root of all evil.

    Olive in Italy

    Moray Dalton

  • The words were an echo of those which formed the mainspring of the Admiral's life.

  • For that was really the mainspring of her fantastic actions.

    The Good Soldier

    Ford Madox Ford

British Dictionary definitions for mainspring

mainspring

noun
  1. the principal power spring of a mechanism, esp in a watch or clock
  2. the chief cause or motive of something
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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

Word Origin and History for mainspring

n.

1590s, of watches, clocks, etc., from main (adj.) + spring (n.3). Figurative use from 1690s.

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Online Etymology Dictionary, © 2010 Douglas Harper