impenetrability

If on the contrary they join impenetrability to the three dimensions, they are no more talking about something simple.

A sudden shadow passed over his face, giving it a strange pallor and impenetrability.

Sydney Smith's aspersions upon the impenetrability of the Scotch skull are well known, though their justice may be questioned.

Nothing could help it on better with the public than the impenetrability of the secret attached to it.

You wrap yourself in impenetrability and expect the world to be clairvoyant.