¹riddle

mystery, problem, enigma, riddle, puzzle mean something which baffles or perplexes. mystery applies to what cannot be fully understood by reason or less strictly to whatever resists or defies explanation <the mystery of the stone monoliths>. problem applies to a question or difficulty calling for a solution or causing concern <problems created by high technology>. enigma applies to utterance or behavior that is very difficult to interpret <his suicide remains an enigma>. riddle suggests an enigma or problem involving paradox or apparent contradiction <the riddle of the reclusive pop star>. puzzle applies to an enigma or problem that challenges ingenuity for its solution <the thief's motives were a puzzle for the police>.