174 entries under adjective topic. ×

2
hearty(strong, fit, healthy, well)
2
immovable
2
incessant(strong, firm, determined, steady)
2
intrepid
2
invincible
2
kinetic(strong, moving, energetic, lively)
2
lively(strong, moving, active, vigorous)
2
plodding(strong, firm, determined, steady)
2
plucky
2
plugging(strong, firm, determined, active)
2
rigid
2
rugged(strong, sound, tough, fit)
2
set
2
spirited(strong, moving, lively, active)
2
strenuous(strong, difficult, energetic, lively)
2
strong-willed
2
tough(strong, sound, fit, firm)
2
trusty(trustworthy, faithful)
2
unchangeable
2
unconquerable
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APASmart Define. (2015). unflagging thesaurus. Retrieved September 25, 2026, from https://smartdefine.org/unflagging/thesaurus/synonyms
ChicagoSmart Define. 2015. "unflagging thesaurus" https://smartdefine.org/unflagging/thesaurus/synonyms (accessed September 25, 2026).
HarvardSmart Define 2015, unflagging thesaurus, Smart Define, viewed 25 September, 2026, <https://smartdefine.org/unflagging/thesaurus/synonyms>.
MLASmart Define. "unflagging thesaurus" 14 April 2015. Web. 25 September 2026. <https://smartdefine.org/unflagging/thesaurus/synonyms>