43 entries under firm topic. ×

35
tireless(adjective, strong, continue, difficult)
27
unflagging(adjective, strong, tough, continue, fit)
25
persistent(adjective, strong, determined, steady)
20
persevering(adjective, strong, difficult, determined)
19
dogged(adjective, strong, determined, steady)
18
determined(adjective, strong, steady, resolute)
16
unfaltering(adjective, strong, determined, steady)
16
unwavering(adjective, set, strong, determined)
15
resolute(adjective, set, strong, determined)
14
tenacious(adjective, strong, tough, fit)
12
unfailing(adjective, set, strong, continue)
12
inexhaustible(adjective, strong, continue, energetic)
12
unwearied(adjective, activity, strong, continue)
11
staunch(adjective, strong, tough, fit)
11
steady(adjective, strong, determined, resolute)
10
unswerving(adjective, set, strong, determined)
9
constant(adjective, strong, determined, steady)
9
indomitable(adjective, strong, determined, steady)
9
pertinacious(adjective, strong, determined, steady)
8
patient(noun, adjective, strong, determined)
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APASmart Define. (2015). indefatigable thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/indefatigable/thesaurus/synonyms
ChicagoSmart Define. 2015. "indefatigable thesaurus" https://smartdefine.org/indefatigable/thesaurus/synonyms (accessed September 24, 2026).
HarvardSmart Define 2015, indefatigable thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/indefatigable/thesaurus/synonyms>.
MLASmart Define. "indefatigable thesaurus" 10 April 2015. Web. 24 September 2026. <https://smartdefine.org/indefatigable/thesaurus/synonyms>