mystery

Synonyms: abstruseness brainteaser braintwister charade chiller cliffhanger closed book conundrum crux cryptogram difficulty enigma grabber inscrutability inscrutableness mindboggler mystification occult oracle perplexity poser problem puzzlement question rebus riddle rune secrecy sixty-four-thousand-dollar question sphinx stickler stumper subtlety teaser thriller tough nut to crack twister whodunit why

Antonyms: known understanding