2
hard-working
2
hearty(adjective, strong, fit, healthy, well)
2
immovable
2
incessant(adjective, strong, firm, determined, steady)
2
incurable
2
intent
2
intrepid
2
invincible
2
kinetic(adjective, strong, moving, energetic, lively)
2
lively(adjective, strong, moving, active, vigorous)
2
permanent
2
plodding(adjective, strong, firm, determined, steady)
2
plucky(adjective, tenacious)
2
plugging(adjective, strong, firm, determined, active)
2
rigid
2
rugged(adjective, strong, sound, tough, fit)
2
set
2
spirited(adjective, strong, moving, lively, active)
2
strenuous(adjective, strong, difficult, energetic, lively)
2
strong-willed(adjective, tenacious)
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APASmart Define. (2015). unflagging thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/unflagging/thesaurus/synonyms
ChicagoSmart Define. 2015. "unflagging thesaurus" https://smartdefine.org/unflagging/thesaurus/synonyms (accessed September 22, 2026).
HarvardSmart Define 2015, unflagging thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/unflagging/thesaurus/synonyms>.
MLASmart Define. "unflagging thesaurus" 14 April 2015. Web. 22 September 2026. <https://smartdefine.org/unflagging/thesaurus/synonyms>