not penetrable; that cannot be penetrated, pierced, entered, etc.
inaccessible to ideas, influences, etc.
incapable of being understood; inscrutable; unfathomable: an impenetrable mystery.
Physics. possessing impenetrability.

Origin of impenetrable

1425–75; late Middle English impenetrabel < Latin impenetrābilis. See im-2, penetrable
Related formsim·pen·e·tra·ble·ness, nounim·pen·e·tra·bly, adverb

Synonyms for impenetrable

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

Examples from the Web for impenetrably

Contemporary Examples of impenetrably

  • “In this country that we were told was impenetrably dangerous, guys were just turning up,” he said.

    The Daily Beast logo
    Iraq, Under the Boot

    Jace Lacob

    October 15, 2009

Historical Examples of impenetrably

  • The rushlight had burned out and the cell was impenetrably dark.

    Micah Clarke

    Arthur Conan Doyle

  • "Till nine o'clock or a little after," suggested Mrs. Travers, impenetrably.

    The Rescue

    Joseph Conrad

  • But Wilkins was as impenetrably suave as he had been the day before.

    The Search Party

    G. A. Birmingham

  • It was a cold, rainy, and impenetrably dark night on the tow-path.

  • The choir is impenetrably dark most of the year at this early hour.

British Dictionary definitions for impenetrably



incapable of being pierced through or penetratedan impenetrable forest
incapable of being understood; incomprehensibleimpenetrable jargon
incapable of being seen throughimpenetrable gloom
not susceptible to ideas, influence, etcimpenetrable ignorance
physics (of a body) incapable of occupying the same space as another body
Derived Formsimpenetrability, nounimpenetrableness, nounimpenetrably, adverb
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 impenetrably



mid-15c., from Middle French impenetrable, from Latin impenetrabilis "that cannot be penetrated," from assimilated form of in- "not, opposite of" (see in- (1)) + penetrabilis "penetrable" (see penetrate). Related: Impenetrably; impenetrability.

Online Etymology Dictionary, © 2010 Douglas Harper