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

Origin of impregnable

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

Synonyms for impregnable

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

Antonyms for impregnable Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for impregnability

Contemporary Examples of impregnability

Historical Examples of impregnability

  • If any spot can impress the notion of impregnability it is Kuffstein.

  • Of course his impregnability gave rise to all manner of stories.

    The New Tenant

    E. Phillips Oppenheim

  • But its impregnability could not offset its gross imprudence.

    Benjamin Franklin

    John Torrey Morse, Jr.

  • These were old and had not been repaired, since the Saguntines trusted in the impregnability of the steeps.


    Vicente Blasco Ibez

  • If any spot can impress the notion of impregnability, it is Kuffstein.

British Dictionary definitions for impregnability




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

Word Origin for impregnable

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



impregnatable (ˌɪmprɛɡˈneɪtəbəl)


able to be impregnated; fertile
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 impregnability



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.

Online Etymology Dictionary, © 2010 Douglas Harper