64 entries under serious topic. ×

1
desperate(severe, significant, critical, grave)
1
determining(big, important, significant, substantial)
1
dire(adjective, severe, heavy, important, significant)
1
earth-shaking(important, significant, critical, historic)
1
earth-shattering(important, significant, critical, historic)
1
hazardous(adjective, heavy, significant, acute)
1
importunate(adjective, big, important, significant, substantial)
1
instant(adjective, important, essential, critical)
1
life and death(expression, idiom, great, important)
1
life or death(expression, adjective, idiom, important)
1
major-league(great, important)
1
perilous(adjective, heavy, significant, acute)
1
preeminent(adjective, great, top, important)
1
star(great, important, key, chief)
1
stellar(great, important, key, chief)
1
sudden
0
afflictive(adjective, severe, heavy, acute)
0
grievous(adjective, great, heavy, important, significant)
0
heavyweight(great, important)
0
highest(basic, prime, key, chief)
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APASmart Define. (2015). vital thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/vital/thesaurus/synonyms
ChicagoSmart Define. 2015. "vital thesaurus" https://smartdefine.org/vital/thesaurus/synonyms (accessed September 29, 2026).
HarvardSmart Define 2015, vital thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/vital/thesaurus/synonyms>.
MLASmart Define. "vital thesaurus" 2 November 2015. Web. 29 September 2026. <https://smartdefine.org/vital/thesaurus/synonyms>