impenetrableness

[RobertFaw]

incomprehensibility by virtue of being too dense to understand

[KalanNug 0]

Impenetrableness is the characteristic or state of being impossible to pass through or enter. It can also refer to the quality of being inscrutable or impossible to understand. In a broader context, it can be used to describe something or someone that is difficult to influence or affect.

[IsobelHaups]

the quality of being impenetrable; impenetrability