Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- adj. Impossible to capture or enter by force: an impregnable fortress.
- adj. Difficult or impossible to attack, challenge, or refute with success: an impregnable argument.
- adj. Capable of being impregnated.
Century Dictionary and Cyclopedia
- Not pregnable; not to be taken or reduced by force: as, an impregnable fortress.
- Not to be moved, shaken, or overcome; invincible: as, impregnable virtue.
Wiktionary
- adj. Too strong to be penetrated.
GNU Webster's 1913
- adj. Not to be stormed, or taken by assault; incapable of being subdued; able to resist attack; unconquerable.
- adj. Capable of being impregnated, as the egg of an animal, or the ovule of a plant.
WordNet 3.0
- adj. incapable of being overcome, challenged or refuted
- adj. immune to attack; incapable of being tampered with
- adj. capable of conceiving
Etymologies
- Middle English imprenable, from Old French : in-, not (from Latin in-; see in-1) + prenable, pregnauble, pregnable; see pregnable.impregn(ate) + -able.
Examples
“Charleston is a strongly fortified place and I think impregnable from the water side.”
Letter from Wright M. Carter to Young J. and Mollie Allen,May 6, 1861
“Given the regular news reports of enterprise data lost through laptop theft, third party misfeasance, WEP hacking, loss of backup tapes, disgruntled employees, etc., it’s not like enterprise data is currently held in impregnable Kryptonite fortresses.”
“It was this land side, containing the citadel and other works, which so impressed outsiders with the idea of impregnable strength.”
“You will storm that great fortress which men call impregnable -- you will storm it and you will vanquish it; and you will come home crowned with glory and honour!”
“I also knew that if we could by any means defend this doorway the murderers could get in nowhere else; for the palace is absolutely impregnable, that is, since the secret door by which Sorais had entered on that memorable night of attempted murder had, by Nyleptha's order, been closed up with masonry.”
“So he built an "impregnable" fortress atop the rock.”
“And never fear: the harmless, "impregnable" Iranians will be more than happy to aid their Shia religious brethren to victory in that battle.”
“Metcalfe said her department had put into place an "impregnable" security system which had been breached.”
“The greatest victory of the last year was, of course, the successful breach on June 6, 1944, of the German "impregnable" seawall of Europe and the victorious sweep of the Allied forces through France and Belgium and Luxembourg -- almost to the Rhine itself.”
“Not that I subscribe to a view which you will often hear: that if Japan once gets the Phillipines, Singapore, Rangoon, and the Netherland Indies, she will be established in an "impregnable" position in the South West Pacific.”
Lists
These user-created lists contain the word ‘impregnable’.
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GRE Barrons Wordlist
A complete Barron's Wordlist for GRE preparation. Your online flashcard replacement.
abase, abash, abate, abbreviate, abdicate, aberrant, aberration, abet, abeyance, abhor, abject, abjure and 4084 more...
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Words with that horrible 'gn' sound
pregnant, interregnum, impregnable, signal, signature, prognosis, ignorant, ignominious, magnum, diagnosis, designation, incognito and 37 more...
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Summers Vocabulary # 2
jejune, ingratiate, congruent, cryptic, beleaguer, tangential, impregnable, predilection, surly, dolorous, untoward, renege

oroboros See unbearable. Mar 9, 2010
madmouth better yet, the two meanings of "inflammable"--that which isn't flammable; that which can be inflamed. May 21, 2009
seanahan I think there are two different prefixes which both look like "im". The first is "not", and the second is roughly "in". Apr 2, 2008
chained_bear It seems awfully weird that impregnable and impregnate mean kind of opposite things. You'd think it would better be inimpregnable. Apr 2, 2008
gtss (Mumm-Ra / "THE UNHOLY ALLIANCE")
"SkyTomb is impregnable"
-Chilla,"MUMM-RA LIVES - PART III" Mar 18, 2008
oroboros Contronymic in the sense: impossible to penetrate vs. penetrable, suseptible to impregnation. Jan 31, 2007