nieprzenikniony angolul:

He was a quiet, inscrutable man

"She's inscrutable even to people who know her extremely well."

Of course, it also sometimes happens that a dream remains entirely inscrutable even after an hour of intense discussion.

impenetrable darkness; an impenetrable jungle

sort of impenetrable, and you can't understand they behaviours (The piano characters)

1) Outside, the fog was thick and impenetrable. an impenetrable barrier 2) Some of the lyrics on their latest album are completely impenetrable