adj. Function: adjective
1
Synonyms: IMPASSABLE 1, impermeable, imperviable, impervious, unpierceable
Related Words: firm, solid, substantial
Antonyms: penetrable
2
Synonyms: INCOMPREHENSIBLE 1, incognizable, uncomprehensible, unfathomable, ungraspable, unintelligible, unknowable
Antonyms: penetrable
3
Synonyms: MYSTERIOUS , arcane, cabalistic, inscrutable, mysterial, mystic, numinous, unaccountable, unguessed, unknowable