cryptic

"the new insurance policy is written without cryptic or mysterious terms"; "a deep dark secret"; "the inscrutable workings of Providence"; "in its mysterious past it encompasses all the dim origins of life"- Rachel Carson; "rituals totally mystifying to visitors from other lands"

"cabalistic symbols engraved in stone"; "cryptic writings"; "thoroughly sibylline in most of his pronouncements"- John Gunther

"a cryptic note"