32 entries under rigorous topic. ×

1
powerful(adjective, severe, harsh, stiff, rigid)
1
rigid(adjective, strong, hard, tough, severe)
1
rough(adjective, strong, hard, tough, severe)
1
severe(adjective, strong, hard, tough, harsh)
1
stiff(adjective, severe, harsh, rigid, tight)
1
strict(adjective, strong, hard, tough, severe)
1
tough(adjective, strong, hard, severe, harsh)
1
unsparing(adjective, strong, hard, tough, harsh)
1
valid(adjective, severe, harsh, stiff, rigid)
0
forceful(adjective, severe, stiff, tight, strict)
0
nit-picking(adjective, harsh, rigid, strict, thorough)
0
tight(adjective, severe, stiff, rigid, strict)
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APASmart Define. (2013). by the book thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/by_the_book/thesaurus/synonyms
ChicagoSmart Define. 2013. "by the book thesaurus" https://smartdefine.org/by_the_book/thesaurus/synonyms (accessed September 29, 2026).
HarvardSmart Define 2013, by the book thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/by_the_book/thesaurus/synonyms>.
MLASmart Define. "by the book thesaurus" 19 May 2013. Web. 29 September 2026. <https://smartdefine.org/by_the_book/thesaurus/synonyms>