Synonyms 1. secret, esoteric, occult, cryptic. Mysterious, inscrutable, mystical, obscure refer to that which is not easily comprehended or explained. That which is mysterious by being unknown or puzzling, excites curiosity, amazement, or awe: a mysterious disease.Inscrutable applies to that which is impenetrable, so enigmatic that one cannot interpret its significance: an inscrutable smile. That which is mystical has a secret significance, such as that attaching to certain rites or signs: mystical symbols. That which is obscure is discovered or comprehended dimly or with difficulty: obscure motives.3. unfathomable, unintelligible, incomprehensible, enigmatic, impenetrable.