- Definitions|1
- Thesaurus|74
- Abbreviations|0
15 entries under challenge topic. ×
| enigma(noun, trouble, question, secret) | |
| mystery(noun, trouble, difficulty, question) | |
| riddle(noun, trouble, question, secret) | |
| conundrum(noun, trouble, question, secret) | |
| secret(noun, trouble, question, puzzle) | |
| brain-teaser(noun, trouble, puzzle, mystery) | |
| mystification(noun, trouble, question, secret) | |
| problem(noun, trouble, question, secret) | |
| puzzlement(noun, trouble, question, secret) | |
| poser(noun, trouble, question, secret) | |
| puzzle(noun, trouble, question, secret) | |
| why(noun, trouble, difficulty, question) | |
| crux(noun, trouble, difficulty, question) | |
| dilemma(noun, trouble, puzzle) | |
| head-scratcher(noun, trouble, brainteaser) |
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| APA | Smart Define. (2016). closed book thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/closed_book/thesaurus/synonyms |
| Chicago | Smart Define. 2016. "closed book thesaurus" https://smartdefine.org/closed_book/thesaurus/synonyms (accessed September 24, 2026). |
| Harvard | Smart Define 2016, closed book thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/closed_book/thesaurus/synonyms>. |
| MLA | Smart Define. "closed book thesaurus" 31 March 2016. Web. 24 September 2026. <https://smartdefine.org/closed_book/thesaurus/synonyms> |