im ‧ pen ‧ e ‧ tra ‧ ble /ɪmˈpenətrəb ə l, ɪmˈpenɪtrəb ə l/ BrE AmE adjective
1 . impossible to get through, see through, or get into:
The trees formed a dark and impenetrable barrier.
the impenetrable blackness of the night
2 . very difficult or impossible to understand:
impenetrable legal jargon
—impenetrably adverb
—impenetrability /ɪmˌpenətrəˈbɪləti, ɪmˌpenɪtrəˈbɪləti/ noun [uncountable]