80 entries under firm topic. ×

2
regular(adjective, solid, stable, fixed)
2
safe(adjective, calm, strong, complete, secure)
2
staid(adjective, solid, big, heavy)
2
unwavering(adjective, calm, strong, secure)
1
abiding(adjective, calm, strong, secure, tough)
1
brick-wall(adjective, calm, strong, secure)
1
calm(adjective, quiet, strong, light, secure)
1
capable(adjective, strong, sound, tough, fit)
1
equable(adjective, calm, strong, secure)
1
even(adjective, calm, strong, secure)
1
incompressible(adjective, density)
1
poised(adjective, calm, strong, secure)
1
serene(adjective, calm, quiet, light, smooth)
1
set in stone(expression, adjective, idiom, calm, strong)
1
solid as a rock(expression, adjective, idiom, calm, strong)
1
unchangeable(adjective, calm, strong, secure)
1
uniform(adjective, calm, strong, secure)
0
unvarying(adjective, calm, strong, secure)
0
allegiant(adjective, solid, stable, fixed)
0
ardent(adjective, solid, enthusiastic, vigorous)
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APASmart Define. (2016). substantial thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/substantial/thesaurus/synonyms
ChicagoSmart Define. 2016. "substantial thesaurus" https://smartdefine.org/substantial/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2016, substantial thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/substantial/thesaurus/synonyms>.
MLASmart Define. "substantial thesaurus" 24 March 2016. Web. 24 September 2026. <https://smartdefine.org/substantial/thesaurus/synonyms>