15 entries under serious topic. ×

15
important(adjective, substantial, valuable)
10
significant(adjective, important, substantial, unimportant)
10
major(adjective, dull, big, substantial)
10
substantial
9
consequential(adjective, small, substantial)
9
essential(adjective, substantial)
8
weighty(adjective, light, important, substantial)
5
meaningful(adjective, substantial, little, meaningless)
4
useful(adjective, substantial)
4
valuable(adjective, substantial)
4
worthwhile(adjective, substantial)
1
relevant(adjective, insignificant, substantial, unrelated)
1
necessary(adjective, substantial, unimportant)
1
pertinent(adjective, substantial)
0
uncommon(adjective, substantial)
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APASmart Define. (2015). trivial thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/trivial/thesaurus/antonyms
ChicagoSmart Define. 2015. "trivial thesaurus" https://smartdefine.org/trivial/thesaurus/antonyms (accessed September 30, 2026).
HarvardSmart Define 2015, trivial thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/trivial/thesaurus/antonyms>.
MLASmart Define. "trivial thesaurus" 10 April 2015. Web. 30 September 2026. <https://smartdefine.org/trivial/thesaurus/antonyms>