115 entries under heavy topic. ×

1
effortful(adjective, hard, tough, severe, rough)
1
exacting(adjective, hard, tough, severe, rough)
1
exceptional(adjective, great, big, unusual)
1
exhausting(adjective, hard, tough, severe, rough)
1
exigent(adjective, hard, tough, difficult, big)
1
fatiguing(adjective, tough, severe, rough, difficult)
1
four-star
1
front-page(great, big, significant, substantial)
1
hairy(adjective, bad, rough, difficult)
1
high-power
1
irksome(adjective, tough, severe, rough, difficult)
1
labored(adjective, hard, tough, severe, rough)
1
life and death(expression, idiom, great, important)
1
mean(adjective, tough, rough, difficult, unpleasant)
1
merciless(adjective, tough, severe, rough, difficult)
1
obscure(adjective, dull, dark, gloomy)
1
playing hard ball(expression, adjective, idiom, great)
1
pre-eminent
1
professional(great, practical, controlled, orderly)
1
scabrous(adjective, tough, rough, difficult)
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APASmart Define. (2016). serious thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/serious/thesaurus/synonyms
ChicagoSmart Define. 2016. "serious thesaurus" https://smartdefine.org/serious/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2016, serious thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/serious/thesaurus/synonyms>.
MLASmart Define. "serious thesaurus" 24 February 2016. Web. 27 September 2026. <https://smartdefine.org/serious/thesaurus/synonyms>