Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- adj. Impossible to penetrate or enter: an impenetrable fortress.
- adj. Impossible to understand; incomprehensible: impenetrable jargon.
- adj. Impervious to sentiment or argument: an impenetrable heart.
Century Dictionary and Cyclopedia
- Incapable of being penetrated; not penetrable, in any sense of that word.
- Specifically, in physics, having the property of preventing any other substance from occupying the same place at the same time.
Wiktionary
- adj. Not penetrable.
- adj. figuratively Incomprehensible; inscrutable.
GNU Webster's 1913
- adj. Incapable of being penetrated or pierced; not admitting the passage of other bodies; not to be entered; impervious.
- adj. (Physics) Having the property of preventing any other substance from occupying the same space at the same time.
- adj. Inaccessible, as to knowledge, reason, sympathy, etc.; unimpressible; not to be moved by arguments or motives.
WordNet 3.0
- adj. not admitting of penetration or passage into or through
- adj. permitting little if any light to pass through because of denseness of matter
- adj. impossible to understand
Etymologies
- From Latin impenetrabilis. (Wiktionary)
Examples
“Announcing his response to a formal consultation, Cable outlined plans for greater diversity on boards – including requiring boards to contain two people who had never had seats in boardrooms before – and to make remuneration reports, which he described as "impenetrable", easier to understand.”
The Guardian: Vince Cable hands shareholders power to tackle executive pay
“It was not in impenetrable shadow as the other objects in the yard were, but had a dismal light about it, like a bad lobster in a dark cellar.”
A Christmas Carol by Charles Dickens, Stave 1 Marley’s Ghost | Solar Flare: Science Fiction News
“Even this strong man shrank from this idea and showed a very natural recoil as his glances flew about the ill-omened room and finally rested on the fireside over which so repellent a mystery hung in impenetrable shadow.”
“Like a cloud, like one of many that were spread in impenetrable woof over the sky, which, when the shepherd north has driven its companions "to drink Antipodean noon," fades and dissolves in the clear ether -- Such were we!”
“From that moment the primate of Egypt disappeared from the eyes of his enemies, and remained above six years concealed in impenetrable obscurity.”
“The only reason to write legislation in impenetrable legalize is a desire to hide what they’re doing from their constituents and one another (and, I suppose, tradition, upheld to preserve their ability to hide what they’re doing in the future.”
“The supreme confidence of the Romney organization - one advisor called his Florida firewall "impenetrable" - has been shaken in recent days by the former Massachusetts governor's repeated stumbles over his personal taxes.”
“No helmet prevented a head struck by the edges of the Crusaders 'swords from being wounded; and they found the stitching of their so-called impenetrable cuirasses too fragile.”
“ACE said it had consulted widely and feedback had included complaints that the current funding process was "impenetrable" and "a closed shop".”
“Philip Alston of the UN Human Rights Council charges that secret "international intelligence services" allied with local militias are killing Afghan civilians and then hiding behind an "impenetrable" wall of bureaucracy.”
Lists
These user-created lists contain the word ‘impenetrable’.
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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 4087 more...
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Dominant/Submissive
abusive, adamant, autocratic, bossy, bullheaded, bumptious, certain, cock-a-hoop, cocksure, cocky, commanding, compelling and 189 more...
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Interesting words
A list of words that are odd or words that I have looked up.
concupiscence, brize, scree, scoria, forestaff, spanaemia, valetudinarianism, distasture, pyrethrum, laudanum, gentian, bicameral and 11250 more...
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five syllables
ontogenesis, phylogenesis, concatenation, androgenesis, extra textual, inexorably, spagyrically, apophenia, iatrochemist, monocotyloid, morphological, parthenogenic and 998 more...
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words/phrases I wish I could find mor...
puttin' on the dog, smarty, smarty ha..., murgatroyd, treshstra, puissance, corpuscle, socker kaka, peckish, hullabaloo, salvo, holy guacamole, b..., cascade and 112 more...
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The Sog Collection
My big word list.
chaos, flaccid, empirical, flotsam, cacophony, grumble, assuage, awe, romance, mortality, coalesce, fortuitous and 3282 more...
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The Last Werewolf
This novel by Glen Duncan, aside from being a ripping yarn and beautifully written, is just littered with words that I had to look up and discover that often his use of the word not only fitted per...
gurns, bok, chimney breast, dichotomy, Platonic form, filthy, Platonic Form, mathematics, BAM, skirls, clarity, blundering and 298 more...
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Misc. Words.
Words I like to use, words I like but may forget.
corrosion, astonish, solace, ferment, continuum, kinesthetic, permeate, repose, caprice, cardinal, discourse, surrender and 610 more...
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stpeter's Words
abase, abasement, abashed, abdicate, aberrant, abeyance, abhor, abhorrent, abide, abject, ablation, abnegation and 3536 more...
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wordsmithing part deux
because wordsmith is not a verb.
enmity, incarnate, chignon, nape, solitude, nocturne, decorum, warren, svelte, interstice, serene, charlotte and 488 more...
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ginnylev's Words
neuroplasticity, repudiate, scintilla, ruminate, tautology, ombudsman, exigent, filibuster, grace, ambidextrous, amends, disclosure and 623 more...
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conglomeration
wherewithal, wan, zoonotic, zoonosis, nebulous, nefarious, nascent, quiescent, quell, undercroft, unwitting, unutterable and 658 more...
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ash
ash
abash, abate, abbreviate, abdicate, aberrant, aberration, abet, abeyance, abhor, abide, abject, abjure and 4874 more...
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_mark's list
Words I like!
( personal list, favorite words, randomness )psy, nanobot, success, smack, vibration, microcosmic, springgraph, marksmanship, estranged, homoerotic, flex, fiasco and 1707 more...
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Palabrarium
The delicious wonderful words that I love terribly dearly and without which, the world would be a less inventive and worthwhile place. Also, ostensibly, the reason 1984 and esperanto secretly suck.
panoply, footpad, piccalilli, snickersnee, marl, hispid, greengage, slumgullion, golliwog, mumbletypeg, circumlocution, quiescent and 366 more...
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jane's list
newbie list
awake, swept, windy, gusty, lost, floating, disappearing, above, alone, impenetrable, vulnerable, thud and 14 more...
Tweets
Looking for tweets for impenetrable.

Louises "He glazed over. Drifted a moment. Went through something in his impenetrable interior ... "Actually I do know this is hard for you. I'm sorry. I'm not using my imagination. That was my New Year's resolution, you know. Work on standing in the other fellow's shoes. That and to read one poem every day." From "The Last Werewolf" by Glen Duncan. Mar 23, 2012