impenetrable adj.

1 impossible to enter/get through

VERBS appear, be, look, seem | become | find sth They found the jungle virtually impenetrable.

ADV. almost, nearly, virtually

2 impossible to understand

VERBS be, seem | become | remain | find sth

ADV. almost, virtually | somewhat I find his style somewhat impenetrable. | seemingly

PREP. to The language of this document would be impenetrable to anyone except a specialist.