95 entries under hard topic. ×

18
multiple(adjective, difficult, complex)
18
precarious(adjective, difficult, complex)
18
sensitive(adjective, difficult, delicate, complex)
18
severe(adjective, difficult, complex, awkward)
18
sinuous(adjective, difficult, complex)
18
toilsome(adjective, difficult, complex, awkward)
18
trying(adjective, difficult, complex, thorny)
14
convoluted(adjective, simple, fancy, obscure)
14
entangled(verb, adjective, fancy, difficult)
8
abstruse(adjective, fancy, obscure, difficult)
8
obscure(adjective, difficult, complex, sophisticated)
8
perplexing(adjective, fancy, obscure, difficult)
6
deep(adjective, obscure, complex, full)
6
puzzling(adjective, fancy, obscure, difficult)
5
confusing(adjective, complex, tricky, complicated)
5
recondite(adjective, fancy, obscure, difficult)
4
baffling(adjective, difficult, complex, awkward)
4
mixed(adjective, fancy, obscure, difficult)
4
subtle(adjective, obscure, complex, tricky)
3
enigmatic(adjective, obscure, sophisticated, tricky)
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APASmart Define. (2015). involved thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/involved/thesaurus/synonyms
ChicagoSmart Define. 2015. "involved thesaurus" https://smartdefine.org/involved/thesaurus/synonyms (accessed September 26, 2026).
HarvardSmart Define 2015, involved thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/involved/thesaurus/synonyms>.
MLASmart Define. "involved thesaurus" 14 April 2015. Web. 26 September 2026. <https://smartdefine.org/involved/thesaurus/synonyms>