- Definitions|1
- Thesaurus|74
- Abbreviations|0
6 entries under expression topic. ×
| sixty-four-thousand-dollar question(question, secret, puzzle, subtlety) | |
| tough nut to crack(idiom, question, secret, puzzle) | |
| confidential information(perplexity, abstruseness, inscrutableness) | |
| magic number(perplexity, abstruseness, inscrutableness) | |
| privileged information(perplexity, abstruseness, inscrutableness) | |
| skeleton in cupboard(idiom, perplexity, abstruseness, inscrutableness) |
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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> |