| problem(noun, trouble, difficulty, challenge, question) |
| riddle(noun, trouble, difficulty, challenge, question) |
| enigma(noun, trouble, difficulty, challenge, question) |
| conundrum(noun, trouble, difficulty, informal, challenge) |
| mystery(noun, trouble, difficulty, challenge, question) |
| puzzle(noun, difficulty, challenge, question, secret) |
| question(noun, difficulty, secret, puzzle, obscurity) |
| stumper(noun, difficulty, challenge, question, secret) |
| brainteaser(noun, difficulty, challenge, question, secret) |
| model(noun, example) |
| poseur(noun, mimic, dandy, popinjay) |
| perplexity(noun, question, secret, puzzle, mystery) |
| puzzlement(noun, trouble, challenge, question, secret) |
| why(noun, trouble, difficulty, challenge, question) |
| closed book(noun, expression, trouble, challenge, question) |
| example(noun, challenge, question, puzzle, mystery) |
| posturer |
| toughie |
| peacock(noun, dandy, popinjay) |
| sticker |