95 entries under firm topic. ×

1
grim(tough, unreasonable, stubborn, problematic)
1
hard-core(determined, impulsive, stubborn, reckless)
1
hard-nosed(determined, impulsive, obstinate, stubborn)
1
hardened(adjective, hard, tough, solid)
1
hardheaded(tough, unreasonable, grim, inflexible)
1
immalleable(adjective, hard, solid, stiff)
1
impliable(adjective, hard, solid, stiff)
1
indurate(adjective, hard, solid, tense)
1
inelastic(adjective, hard, tough, solid)
1
jelled(adjective, hard, tough, solid)
1
mechanical(adjective, hard, solid, tense)
1
mule(tough, determined, unreasonable, grim)
1
numbed(adjective, hard, solid, tense)
1
ossified(adjective, hard, solid, tense)
1
persevering(adjective, tough, unreasonable, grim)
1
petrified(adjective, hard, solid, tense)
1
rheumatic(adjective, hard, solid, tense)
1
solid(adjective, hard, tough, tense)
1
solidified(adjective, hard, tough, solid)
1
starched(adjective, hard, solid, stiff)
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APASmart Define. (2015). refractory thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/refractory/thesaurus/synonyms
ChicagoSmart Define. 2015. "refractory thesaurus" https://smartdefine.org/refractory/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, refractory thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/refractory/thesaurus/synonyms>.
MLASmart Define. "refractory thesaurus" 10 April 2015. Web. 25 September 2026. <https://smartdefine.org/refractory/thesaurus/synonyms>