52 entries under firm topic. ×

3
intractable(adjective, tough, unreasonable, grim)
3
single-minded(adjective, tough, unreasonable, grim)
3
stiff-necked(adjective, mean, hard, tough)
3
tough(adjective, mean, strong, hard)
2
compact(adjective, set, strong, hard)
2
dogged(adjective, mean, strong, hard, tough)
2
durable(adjective, stiff, rigid)
2
recalcitrant(tough, persistent, obstinate, stubborn)
2
rocky(adjective, set, strong, stiff)
2
solid(adjective, set, strong, hard, tough)
2
thick(adjective, strong, hard, tough)
1
bound(verb, adjective, strong, tough)
1
callous(adjective, set, mean, strong, hard)
1
fixed(adjective, mean, strong, hard, tough)
1
mulish(adjective, mean, strong, hard, tough)
1
perverse(adjective, mean, hard, tough)
1
pigheaded(adjective, mean, hard, tough)
1
rocklike(adjective, stiff, rigid, steel)
1
staunch(adjective, set, strong, hard, tough)
1
stony(adjective, set, strong, hard)
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APASmart Define. (2015). iron thesaurus. Retrieved September 27, 2026, from https://smartdefine.org/iron/thesaurus/synonyms
ChicagoSmart Define. 2015. "iron thesaurus" https://smartdefine.org/iron/thesaurus/synonyms (accessed September 27, 2026).
HarvardSmart Define 2015, iron thesaurus, Smart Define, viewed 27 September, 2026, <https://smartdefine.org/iron/thesaurus/synonyms>.
MLASmart Define. "iron thesaurus" 14 April 2015. Web. 27 September 2026. <https://smartdefine.org/iron/thesaurus/synonyms>