impenetrability's Usage Examples:

Bodies then are triply extended substances, each occupying enough space to prevent mutual penetration, and by this force of mutual impenetrability or interresistance cause one another to form a joint mass with a common velocity whenever they collide.

Thanks to the impenetrability of their fastnesses, they preserved their original savagery longer than any of their neighbours, and this savagery was coupled with a valour so tenacious and enterprising as to make them formidable to all who dwelt near them.

75% of silicon and may have even as little as 1% if impenetrability is so important that softness and consequent ease of machining must be sacrificed to it.

Synonyms:

impenetrableness, incomprehensibility,

Antonyms:

clearness, clarity, comprehensibility,