impenetrable

Synonyms: bulletproof close compact firm hard hermetic impassable impermeable impervious inviolable solid substantial thick unpiercable

Antonyms: clear penetrable permeable porous soft thin

Synonyms: arcane baffling cabalistic dark delphic enigmatic enigmatical hidden incognizable indiscernible inexplicable inscrutable mysterious mystic obscure sibylline unaccountable unfathomable ungraspable unintelligible unknowable

Antonyms: comprehensible intelligible penetrable understandable