2
peppy(adjective, strong, tough, fit, lively)
2
perpetual(adjective, continuous)
2
plugging(adjective, strong, firm, determined, active)
2
purposeful
2
repeated(adjective, continuous)
2
ruthless(adjective, resolute)
2
sprightly(adjective, strong, moving, lively, active)
2
spunky(adjective, resolute, tenacious)
2
stable
2
strong-willed(adjective, resolute, tenacious)
2
unchanging(adjective, continuous)
2
uncompromising(adjective, resolute)
2
unshakable
2
unsleeping
2
unstoppable
2
zippy(adjective, strong, tough, fit, lively)
1
adamant
1
attention
1
attentive
1
ball of fire(expression, adjective, idiom, strong, lively)
11 years ago|10k views|share |citing 
APASmart Define. (2015). indefatigable thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/indefatigable/thesaurus/synonyms
ChicagoSmart Define. 2015. "indefatigable thesaurus" https://smartdefine.org/indefatigable/thesaurus/synonyms (accessed September 23, 2026).
HarvardSmart Define 2015, indefatigable thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/indefatigable/thesaurus/synonyms>.
MLASmart Define. "indefatigable thesaurus" 10 April 2015. Web. 23 September 2026. <https://smartdefine.org/indefatigable/thesaurus/synonyms>