4
accurate(adjective, open, honest, sensible, reliable)
4
devoted(adjective, good, strong, firm, honest)
4
eternal(adjective, continue, certain, steady, fixed)
4
everlasting(adjective, continue)
4
fast(adjective, trustworthy, faithful)
4
fixed(adjective, set, clear, certain, regular)
4
incessant(adjective, strong, continue, firm, determined)
4
perennial(adjective, enduring, perpetual)
4
persisting
4
predictable(adjective, good, strong, solid, steady)
4
sure-fire(adjective, informal, certain, flawless, unquestionable)
4
surefire(adjective, certain, reliable, trustworthy, unquestionable)
4
unchanged(adjective, fixed, even, rigid, uniform)
4
unending(adjective, continue)
3
absolute(adjective, certain, unchanging)
3
honest(adjective, open, sensible, sure, reliable)
3
industrious
3
intact
3
inviolate
3
never-failing(adjective, set, clear, certain, sure)
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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>