| introvert(noun, question, mysterious, secret, puzzle) |
| knotty point(expression, characteristic, strangeness, weirdness) |
| late bloomer(noun, expression, question, mysterious, secret) |
| matter in dispute(expression, characteristic, strangeness, weirdness) |
| moot point(expression, characteristic, strangeness, weirdness) |
| mystery story(expression, characteristic, strangeness, weirdness) |
| nut to crack(expression, characteristic, strangeness, weirdness) |
| open question(expression, characteristic, strangeness, weirdness) |
| outlier(noun, secret, mystery, interesting) |
| paradox(noun, question, mysterious, secret, myth) |
| plain question(expression, characteristic, strangeness, weirdness) |
| point in dispute(expression, characteristic, strangeness, weirdness) |
| question at issue(expression, characteristic, strangeness, weirdness) |
| sealed book(expression, characteristic, strangeness, weirdness) |
| subject of controversy(expression, characteristic, strangeness, weirdness) |
| subject of inquiry(expression, characteristic, strangeness, weirdness) |
| unknown quantity(noun, expression, question, mysterious, secret) |
| conundrum(noun, trouble, challenge, question, mysterious) |
| bolter(noun, issue, question, task) |
| abnormal(adjective, characteristic, strangeness, weirdness) |