impenetrability

UK: /ɪmˌpenɪtrəˈbɪlɪtɪ/

US: /ɪmˌpɛnɪtrəˈbɪlɪti/

US: (im pen′i trə bil′i tē, im′pen-)

WordReference Random House Unabridged Dictionary of American English © 2025

im•pen•e•tra•bil•i•ty  (im pen′i trə bil′i tē, im′pen-), n. 

1. the state or quality of being impenetrable.
2. Physics that property of matter by virtue of which two bodies cannot occupy the same space simultaneously.

• impenetr(able) + -ability 1655–65

WordReference Random House Learner's Dictionary of American English © 2025

im•pen•e•tra•ble /ɪmˈpɛnɪtrəbəl/   adj. 

1. that cannot be penetrated:
   an impenetrable barrier.
2. that cannot be understood:
   an impenetrable mystery.

im•pen•e•tra•bil•i•ty /ɪmˌpɛnɪtrəˈbɪlɪti/  n. [uncountable]
im•pen•e•tra•bly, adv.

WordReference Random House Unabridged Dictionary of American English © 2025

im•pen•e•tra•ble  (im pen′i trə bəl), adj. 

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.
4. Physics possessing impenetrability.

• Latin impenetrābilis. See im-², penetrable
• late Middle English impenetrabel 1425–75

im•pen′e•tra•ble•ness, n. 
im•pen′e•tra•bly,
adv Synonyms

• 3. incomprehensible, mysterious, obscure, hidden.

Antonyms

• 3. clear, lucid.