impenetrable Synonyms

heavy unfathomable impregnable dense thick soupy solid sibylline serried thickened tough trackless unaccessible unaccountable unpassable unpenetrable vitrified wayless secretive sealed invulnerable irresolvable jellied jungly mysterious mystic mystifying obscure occult opaque overgrown pathless perplexing plumbic puzzling recondite resistant involved weatherproof wildering unattackable undefeatable unclear unprocurable rainproof rocklike unscalable unanalyzable un-come-at-able uncomprehensible