secret synonyms

dark deep strange unknown hidden mysterious obscure ambiguous mystical clouded veiled occult mystic esoteric cryptic unintelligible arcane abstruse unenlightened recondite cabalistic classified enigmatical

close confidential sly disguised covert enigmatic undercover undisclosed camouflaged underhand taciturn incognito stealthy backdoor backstairs clandestine furtive surreptitious underhanded unrevealed cryptographic