adj.
VERBS
▪ be , seem
▪ become
▪ remain
▪ find sth
▪
They found the jungle virtually ~.
ADVERB
▪ almost , nearly , virtually
▪
His reports were virtually ~ without an explanation.
▪ seemingly
PREPOSITION
▪ to
▪
The language of this document would be ~ to anyone except a specialist.
Impenetrable is used with these nouns: ↑ barrier , ↑ forest , ↑ fortress , ↑ jargon , ↑ jungle , ↑ mystery