Webster’s Revised Unabridged Dictionary · 1913
Impenetrability
Im·pen′e·tra·bil′i·ty (ĭm·pĕn′ē·trȧ·bĭl′ĭ·ty̆), n. [Cf. F. impénétrabilité.] 1. Quality of being impenetrable.
2. (Physics) That property in virtue of which two portions of matter can not at the same time occupy the same portion of space.
3. Insusceptibility of intellectual or emotional impression; obtuseness; stupidity; coldness.