Synonyms for riddle

noun

1. A difficult problem

   problem, puzzle, question, knotty question, doubt, quandary, entanglement, dilemma, embarrassment, perplexity, enigma, confusion, complication, complexity, intricacy, strait, labyrinth, predicament, plight, distraction, bewilderment; see also puzzle 2.

   Antonyms simplicity*, clarity, disentanglement.

2. An obscure question to be solved for amusement

   mystery, conundrum, puzzle, enigma, charade, rebus, brain teaser, brain twister.

   Antonyms answer*, solution, explanation. See syn. study at puzzle.puzzle.