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.

Nearby words

  1. impeller,
  2. impend,
  3. impendent,
  4. impending,
  5. impenetrability,
  6. impenitence,
  7. impenitent,
  8. impennate,
  9. imper.,
  10. imperatival

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

Examples from the Web for impenetrable

British Dictionary definitions for impenetrable



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 impenetrable



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