- Definitions|1
- Thesaurus|74
- Abbreviations|0
27 entries under difficulty topic. ×
| mystery(noun, trouble, challenge, question) | |
| why(noun, trouble, challenge, question) | |
| crux(noun, trouble, challenge, question) | |
| abstruseness(question, secret, puzzle, subtlety) | |
| brainteaser(question, secret, puzzle, subtlety) | |
| braintwister(question, secret, puzzle, subtlety) | |
| chiller(question, secret, puzzle, subtlety) | |
| cliffhanger(question, secret, puzzle, obscurity) | |
| cryptogram(question, secret, puzzle, obscurity) | |
| grabber(question, secret, puzzle, perplexity) | |
| inscrutability(question, secret, puzzle, subtlety) | |
| inscrutableness(question, secret, puzzle, subtlety) | |
| mindboggler(question, secret, puzzle, subtlety) | |
| occult(question, secret, puzzle, subtlety) | |
| oracle(question, secret, puzzle, subtlety) | |
| perplexity(noun, question, secret, puzzle) | |
| question(secret, puzzle, obscurity, subtlety) | |
| rune(question, secret, puzzle, subtlety) | |
| secrecy(question, secret, puzzle, obscurity) | |
| sphinx(question, secret, puzzle, perplexity) |
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| APA | Smart Define. (2016). closed book thesaurus. Retrieved September 21, 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 21, 2026). |
| Harvard | Smart Define 2016, closed book thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/closed_book/thesaurus/synonyms>. |
| MLA | Smart Define. "closed book thesaurus" 31 March 2016. Web. 21 September 2026. <https://smartdefine.org/closed_book/thesaurus/synonyms> |