2
indomitable(adjective, strong, firm, determined, steady)
2
inerrant(certain, unquestionable, undisputable)
2
interminable(adjective, continue)
2
lasting(adjective, certain, fixed, reliable, continuous)
2
nonstop(adjective, continue)
2
ongoing(adjective, continue)
2
plodding(adjective, strong, firm, determined, steady)
2
plugging(adjective, strong, firm, determined, steady)
2
positive(adjective, good, clear, strong, solid)
2
purposeful
2
responsible(adjective, good, honest, sensible, solid)
2
static(set, regular, fixed, constant, rigid)
2
staying
2
straight(adjective, open, honest, solid, certain)
2
strong(adjective, good, firm, honest, solid)
2
tried-and-true(adjective, good, strong, honest, solid)
2
true-blue(adjective, good, strong, open, honest)
2
true blue(honest, sensible, realistic, reliable, mature)
2
unaltered(adjective, uniform, unchanging, unchanged)
2
unbroken
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APASmart Define. (2016). unfailing thesaurus. Retrieved September 28, 2026, from https://smartdefine.org/unfailing/thesaurus/synonyms
ChicagoSmart Define. 2016. "unfailing thesaurus" https://smartdefine.org/unfailing/thesaurus/synonyms (accessed September 28, 2026).
HarvardSmart Define 2016, unfailing thesaurus, Smart Define, viewed 28 September, 2026, <https://smartdefine.org/unfailing/thesaurus/synonyms>.
MLASmart Define. "unfailing thesaurus" 3 March 2016. Web. 28 September 2026. <https://smartdefine.org/unfailing/thesaurus/synonyms>