| cross-word puzzle(noun, expression, difficult, issue, secret) |
| dark secret(noun, expression, secret, puzzle, mystery) |
| incertitude(noun, issue, doubt, question) |
| inconclusiveness(noun, issue, doubt, question) |
| ink crossword(noun, expression, difficult, issue, secret) |
| magic number(expression, confidence, secret, puzzle, mystery) |
| mindboggler(noun, issue, doubt, question) |
| pictorial puzzle(noun, expression, difficult, issue, secret) |
| privacy(noun, secret, puzzle, mystery, riddle) |
| skeleton in cupboard(expression, idiom, confidence, secret, puzzle) |
| skeleton in the cupboard(expression, idiom, confidence, secret, puzzle) |
| aenigma(noun, question, secret, puzzle, task) |
| anomaly(noun, issue, doubt, question) |
| bitter fleabane(noun, question, secret, puzzle, task) |
| brain-twister(noun, question, secret, puzzle, mystery) |
| brain basher(noun, difficult, issue, puzzle, mystery) |
| brain teaser(noun, question, secret, puzzle, task) |
| chinese puzzle(noun, difficult, issue, puzzle, mystery) |
| difficult problem(noun, question, puzzle, riddle) |
| double meaning(expression, doubt, uncertainty, vagueness, haziness) |