See more synonyms for hair-trigger on
  1. easily activated or set off; reacting immediately to the slightest provocation or cause: a hair-trigger temper.

Origin of hair-trigger

First recorded in 1885–90

hair trigger

  1. a trigger that allows the firing mechanism of a firearm to be operated by very slight pressure.

Origin of hair trigger

First recorded in 1815–25 Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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Contemporary Examples of hair-trigger

Historical Examples of hair-trigger

British Dictionary definitions for hair-trigger

hair trigger

  1. a trigger of a firearm that responds to very slight pressure
  2. informal
    1. any mechanism, reaction, etc, set in operation by slight provocation
    2. (as modifier)a hair-trigger temper
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 hair-trigger

1830, originally a secondary trigger in a firearm which sprung free a mechanism (hair) which, when set, allowed the main trigger (n.) to be released by very slight force. Figurative use by 1841.

Online Etymology Dictionary, © 2010 Douglas Harper