adj. 25B6; adjective MYSTERIOUS, secret, covert, clandestine; enigmatic, esoteric, obscure, abstruse, recondite, recherché, impenetrable, opaque.
ARCANE
Meaning of ARCANE in English
Concise Oxford thesaurus English vocabulary. Краткий оксфордский словарь английского языка тезаурус. 2012