918 entries under adjective topic. ×

24
laborious(hard, easy, difficult, important)
23
sedate(calm, dull, cool, severe)
22
painful(bad, hard, difficult, offensive)
22
staid(calm, dull, set, cool)
21
dire(hard, difficult, complex)
21
heavyweight(hard, difficult, important, complex)
21
operose(hard, difficult, important, complex)
21
precarious(hard, difficult, complex, dangerous)
20
grim(dull, strong, hard, tough)
20
heartrending(hard, difficult, complex)
20
involved(hard, difficult, complex, awkward)
20
massive(hard, difficult, complex)
20
oppressive(hard, difficult, complex)
20
sore(hard, difficult, complex)
20
stubborn(strong, hard, tough, firm)
20
troubled(hard, difficult, unhappy, gloomy)
19
backbreaking(hard, difficult, complex, awkward)
19
burdensome(hard, difficult, big, heavy)
19
complicated(hard, difficult, complex, awkward)
19
cruel(strong, hard, tough, severe)
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APASmart Define. (2016). serious thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 25 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>