Synonyms|1kAntonyms|253|Broader|5Narrower|1Related|546
3
toilsome(adjective, hard, tough, severe, rough)
3
trying(adjective, heavy)
3
tyrannical(adjective, hard, tough, harsh, cruel)
3
ultra-fine(adjective, feature, slight, difference, subtle)
3
uphill(adjective, hard, tough, severe, rough)
3
veracious(adjective, correct, right, appropriate, honest)
2
absolute
2
abstemious
2
abstinent
2
alert(thoughtful, sober, cautious, prudent, wary)
2
antagonistic(adjective, tough, severe, harsh, grim)
2
assiduous(thoughtful, sober, cautious, prudent, wary)
2
cast-iron
2
censorious(adjective, severe)
2
chilly(adjective, severe)
2
choosy(adjective, thoughtful, precise, sober, prudent)
2
cold(adjective, tough, severe, harsh, cruel)
2
complex
2
concrete(adjective, correct, solid, exact, proper)
2
cool(adjective, severe, thoughtful, sober, cautious)
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ChicagoSmart Define. 2016. "rigorous thesaurus" https://smartdefine.org/rigorous/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2016, rigorous thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/rigorous/thesaurus/synonyms>.
MLASmart Define. "rigorous thesaurus" 26 February 2016. Web. 22 September 2026. <https://smartdefine.org/rigorous/thesaurus/synonyms>