impenetrable
Americanadjective
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not penetrable; that cannot be penetrated, pierced, entered, etc.
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inaccessible to ideas, influences, etc.
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incapable of being understood; inscrutable; unfathomable.
an impenetrable mystery.
- Synonyms:
- hidden, obscure, mysterious, incomprehensible
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Physics. possessing impenetrability.
adjective
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incapable of being pierced through or penetrated
an impenetrable forest
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incapable of being understood; incomprehensible
impenetrable jargon
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incapable of being seen through
impenetrable gloom
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not susceptible to ideas, influence, etc
impenetrable ignorance
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physics (of a body) incapable of occupying the same space as another body
Other Word Forms
- impenetrability noun
- impenetrableness noun
- impenetrably adverb
Etymology
Origin of impenetrable
1425–75; late Middle English impenetrabel < Latin impenetrābilis. See im- 2, penetrable
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Unai Emery's side are being questioned after winning two of their past six Premier League games, and falling to three home defeats in five matches at the once impenetrable Villa Park.
From BBC • Feb. 26, 2026
That style is dense, intricate and sometimes impenetrable, and Ms. Serpell means to celebrate its difficulties while guiding us through them.
From The Wall Street Journal • Feb. 10, 2026
The primary difference between public and private prisons, experts told Salon, is that private prisons operate in an even more impenetrable black box than public prisons.
From Salon • Jan. 28, 2026
A poorly cleared corner followed by an unfortunate deflection proved fatal to the hitherto impenetrable Parisian defence.
From Barron's • Jan. 20, 2026
The advocates of the new chemistry insisted that they had no time for texts whose meaning was impenetrable.
From "The Invention of Science" by David Wootton
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
