| difficult riddle(noun, expression, trouble, show, difficulty) |
| why(noun, trouble, show, difficulty, challenge) |
| mindboggler(noun, difficulty, question, secret, puzzle) |
| mind-boggler(noun, challenge, doubt, question, uncertainty) |
| mind-breaker(noun, trouble, challenge, puzzle, riddle) |
| difficulty(noun, question, problem, brain) |
| head-scratcher(noun, trouble, show, difficulty, challenge) |
| perplexity(noun, trouble, show, difficulty, challenge) |
| quandary(noun, difficulty, question, problem, brain) |
| vexed question(expression, difficulty, question, problem) |
| anagram(noun, question, amusement, entertainment) |
| brain-twister(noun, informal, question, entertainment) |
| confusing problem(expression, difficulty, question, problem) |
| confusing question(expression, difficulty, question, problem) |
| cruncher(noun, informal, question, problem) |
| facer(noun, informal, question, problem) |
| insoluble problem(expression, trouble, difficulty, problem) |
| intricate problem(expression, issue, question, problem) |
| paradoxical problem(expression, trouble, difficulty, problem) |
| puzzling problem(expression, difficulty, question, problem) |