impenetrableness means the quality of being impenetrable. Lexicurio rates it Sui generis — a strength score of 85 out of 100.
noun
- The quality of being impenetrable.“I need not add, that to a mind of elegance and sensibility, the emblematical allusion which this dress would carry to the secrecy and impenetrableness of the person that wears it, must be the source of a delightful and exquisite sensation.”