3
patient(adjective, strong, firm, determined, steady)
3
perseverant
3
regular(adjective, set, steady, persistent, even)
3
rigid(adjective, set, regular, fixed, constant)
3
round-the-clock(adjective, continue, continual)
3
safe(adjective, good, strong, solid, steady)
3
sedulous
3
timeless(adjective, continue)
3
unfading(fixed, static, unchangeable)
2
abiding(adjective, set, clear, certain, fixed)
2
around-the-clock(adjective, continue)
2
boundless(adjective, certain, unchanging)
2
deadly
2
dedicated(adjective, strong, firm, determined, steady)
2
definite(adjective, good, clear, strong, solid)
2
dyed-in-the-wool(adjective, certain, true, constant, reliable)
2
enduring(adjective, set, clear, certain, steady)
2
guaranteed(adjective, certain, flawless, unquestionable, undisputable)
2
immutable(set, regular, fixed, constant, rigid)
2
imperishable(fixed, continuous, static, unchangeable, everlasting)
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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>