21
sure(adjective, clear, complete, certain, reliable)
19
reliable(adjective, clear, certain, certainty, flawless)
17
unfailing(adjective, certain, flawless, reliable, trustworthy)
17
certain(adjective, certain, reliable, valid, dependable)
13
trustworthy(adjective, certainty, dependable, unfailing, unerring)
12
unerring(adjective, clear, certain, precise, sure)
10
dependable(adjective, certain, flawless, reliable, trustworthy)
8
perfect(adjective, flawless, faultless, dependable, unerring)
7
foolproof(adjective, dependable, unerring)
7
inerrant(adjective, complete, certain, sure, valid)
7
secure(verb, adjective, certain)
7
correct(adjective, perfect, precise, flawless, faultless)
7
exact(adjective, perfect, precise, flawless, faultless)
7
faultless(adjective, perfect, flawless, dependable, unerring)
7
flawless(adjective, perfect, faultless, dependable, unerring)
6
absolute(adjective, certain)
6
accurate(adjective, perfect, certain, precise, flawless)
6
effective(adjective, dependable, unerring)
6
impeccable(adjective, flawless, dependable, unerring)
6
inerrable(adjective, dependable, unerring)
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APASmart Define. (2015). infallible thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/infallible/thesaurus/synonyms
ChicagoSmart Define. 2015. "infallible thesaurus" https://smartdefine.org/infallible/thesaurus/synonyms (accessed September 20, 2026).
HarvardSmart Define 2015, infallible thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/infallible/thesaurus/synonyms>.
MLASmart Define. "infallible thesaurus" 10 April 2015. Web. 20 September 2026. <https://smartdefine.org/infallible/thesaurus/synonyms>