15 entries under trouble topic. ×

27
enigma(noun, challenge, question, secret)
21
mystery(noun, difficulty, challenge, question)
19
riddle(noun, challenge, question, secret)
18
conundrum(noun, challenge, question, secret)
14
secret(noun, challenge, question, puzzle)
12
brain-teaser(noun, challenge, puzzle, mystery)
6
mystification(noun, challenge, question, secret)
6
problem(noun, challenge, question, secret)
6
puzzlement(noun, challenge, question, secret)
4
poser(noun, challenge, question, secret)
4
puzzle(noun, challenge, question, secret)
4
why(noun, difficulty, challenge, question)
2
crux(noun, difficulty, challenge, question)
1
dilemma(noun, challenge, puzzle)
1
head-scratcher(noun, challenge, brainteaser)
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APASmart Define. (2016). closed book thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/closed_book/thesaurus/synonyms
ChicagoSmart Define. 2016. "closed book thesaurus" https://smartdefine.org/closed_book/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, closed book thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/closed_book/thesaurus/synonyms>.
MLASmart Define. "closed book thesaurus" 31 March 2016. Web. 25 September 2026. <https://smartdefine.org/closed_book/thesaurus/synonyms>