| enigma(noun, difficulty, challenge, question, secret) |
| poser(noun, difficulty, challenge, question, secret) |
| problem(noun, difficulty, challenge, question, secret) |
| puzzle(noun, difficulty, challenge, question, secret) |
| riddle(noun, difficulty, challenge, question, secret) |
| conundrum(noun, difficulty, challenge, question, secret) |
| mystery(noun, difficulty, challenge, question, secret) |
| stumper(noun, difficulty, challenge, question, secret) |
| challenge(noun, question, puzzle, mystery, riddle) |
| code(noun, secret) |
| cryptogram(noun, difficulty, question, secret, puzzle) |
| maze(noun, secret) |
| cipher(noun, secret) |
| perplexity(noun, question, secret, puzzle, mystery) |
| teaser(noun, difficulty, challenge, question, secret) |
| trouble(noun, puzzle, riddle, enigma) |
| closed book(noun, expression, question, secret, puzzle) |
| matter(noun, puzzle, riddle, enigma) |
| puzzler(noun, difficulty, challenge, question, puzzle) |
| rebus(noun, question, secret, puzzle, subtlety) |