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Showing results for impenetrable. Search instead for Unpenetrable.
Synonyms

impenetrable

American  
[im-pen-i-truh-buhl] / ɪmˈpɛn ɪ trə bəl /

adjective

  1. not penetrable; that cannot be penetrated, pierced, entered, etc.

  2. inaccessible to ideas, influences, etc.

  3. incapable of being understood; inscrutable; unfathomable.

    an impenetrable mystery.
    Synonyms:
    hidden, obscure, mysterious, incomprehensible
    Antonyms:
    lucid, clear

  4. Physics. possessing impenetrability.

impenetrable British  
/ ɪmˈpɛnɪtrəbəl /

adjective

  1. incapable of being pierced through or penetrated

    an impenetrable forest

  2. incapable of being understood; incomprehensible

    impenetrable jargon

  3. incapable of being seen through

    impenetrable gloom

  4. not susceptible to ideas, influence, etc

    impenetrable ignorance

  5. physics (of a body) incapable of occupying the same space as another body

"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

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.

"I'd be lying if I said I was a completely impenetrable robot," he tells the BBC.

From BBC • Mar. 29, 2026

Dolls, masks, impenetrable shadows: a conjured enigma, all typical Meatyard.

From The Wall Street Journal • Feb. 21, 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 pine trees gave way to a tangled thicket of Brazilian peppers and dense ground scrub, which looked impenetrable.

From "Hoot" by Carl Hiaasen

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.