285 entries under adjective topic. ×

2
hidebound(persistent, obstinate, stubborn, unbending)
2
immovable(strong, hard, tough, difficult)
2
implacable(set, strong, hard, tough)
2
inalterable
2
intent
2
inviolable
2
plodding(strong, firm, determined, steady)
2
plugging(strong, firm, determined, steady)
2
serious(strong, hard, tough, resolute)
2
severe(strong, hard, tough, persistent)
2
steely(set, strong, hard, tough)
2
stoical(calm, cool, tolerant, enduring)
2
thorough
2
true(resolute, tenacious)
2
unbending(strong, hard, tough, difficult)
2
undiscouraged(bold, unconcerned, brave, steadfast)
2
unfailing(strong, firm, determined, steady)
2
unrelenting(set, strong, hard, tough)
2
unremitting(strong, firm, determined, steady)
2
unshakeable
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APASmart Define. (2015). indomitable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/indomitable/thesaurus/synonyms
ChicagoSmart Define. 2015. "indomitable thesaurus" https://smartdefine.org/indomitable/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, indomitable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/indomitable/thesaurus/synonyms>.
MLASmart Define. "indomitable thesaurus" 14 April 2015. Web. 23 September 2026. <https://smartdefine.org/indomitable/thesaurus/synonyms>