infallible

adjectives

incapable of failure or error
"an infallible antidote"; "an infallible memory"; "the Catholic Church considers the Pope infallible"; "no doctor is infallible"
infallible
is derived from
infallibility
antonym
fallible
is similar to
not liable to failure
"a foolproof identification system"; "the unfailing sign of an amateur"; "an unfailing test"
foolproof, unfailing
is similar to
not liable to error
"the Church was...theoretically inerrant and omnicompetent"-G.G.Coulton; "lack an inerrant literary sense"; "an unerring marksman"
inerrable, inerrant, unerring