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  1. strong enough to resist or withstand attack; not to be taken by force, unconquerable: an impregnable fort.
  2. not to be overcome or overthrown: an impregnable argument.
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Origin of impregnable1

1400–50; late Middle English impregnable, imprenable < Middle French, equivalent to im- im-2 + prenable pregnable
Related formsim·preg·na·bil·i·ty, im·preg·na·ble·ness, nounim·preg·na·bly, adverb


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1. invulnerable. 1, 2. See invincible. 2. unassailable.



[im-preg-nuh-buh l]
  1. susceptible to impregnation, as an egg.
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Origin of impregnable2

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Related Words

impenetrable, unassailable, invincible, indestructible, invulnerable, fortified, firm, secure, solid, strong

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British Dictionary definitions for impregnable


  1. unable to be broken into or taken by forcean impregnable castle
  2. unable to be shaken or overcomeimpregnable self-confidence
  3. incapable of being refutedan impregnable argument
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Derived Formsimpregnability or impregnableness, nounimpregnably, adverb

Word Origin

C15 imprenable, from Old French, from im- (not) + prenable able to be taken, from prendre to take


impregnatable (ˌɪmprɛɡˈneɪtəbəl)

  1. able to be impregnated; fertile
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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 impregnable


early 15c., imprenable "impossible to capture," from Middle French imprenable "invulnerable," from assimilated form of in- "not, opposite of" (see in- (1)) + Old French prenable "assailable, vulnerable" (see pregnable). With intrusive -g- 16c., on model of deign, reign, etc. Related: Impregnability.

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Online Etymology Dictionary, © 2010 Douglas Harper