enigma Synonyms

conundrum secret mystery riddle problem brain-teaser closed book ambiguity paradox puzzle obscurity question stealthiness stickler stumper teaser sphinx sticker self-contradiction mystification roun riddled classified information rebus quodlibet quandary twister unknown head scratcher question mark unknown quantity skeleton in the cupboard tough nut to crack secrets braintwister puzzles difficult question brainteaser whodunit why puzzler thriller mystique magic number polysemy jigsaw puzzle Gordian knot koan unsolved problem abstrusity