| confidence(noun, difficult, issue, question, task) |
| confusion(noun, difficult, issue, question, puzzle) |
| doubt(noun, issue, think, question) |
| privity(noun, difficult, issue, question, secret) |
| uncertainty(noun, difficult, issue, doubt, question) |
| brain-teaser orbrain-twister(noun, question, secret, puzzle) |
| braintwister(noun, question, secret, puzzle) |
| double-entendre(noun, question, secret, puzzle) |
| frontiers of knowledge(expression, idiom, secret, mystery, brain-twister) |
| grabber(noun, difficulty, challenge, question, problem) |
| incongruity(noun, difficult, issue, question, task) |
| matter of ignorance(expression, idiom, secret, mystery, brain-twister) |
| mind-twister(noun, question, secret, dilemma, mystery) |
| mist(noun, verb, difficult, issue, think) |
| mysterious puzzle(expression, idiom, secret, mystery, brain-twister) |
| mysteriousness(noun, difficult, issue, question, task) |
| mystery of mysteries(expression, idiom, secret, mystery, brain-twister) |
| proverb(noun, difficult, issue, question, task) |
| question mark(noun, question, secret, dilemma, mystery) |
| quodlibet(noun, difficult, issue, question, task) |