Vine's Expository Dictionary: View Entry
TDNT Reference: 6:174,849
ἄπιστος ápistos, ap'-is-tos; from G1 (as a negative particle) and G4103; (actively) disbelieving, i.e. without Christian faith (specially, a heathen); (passively) untrustworthy (person), or incredible (thing):—that believeth not, faithless, incredible thing, infidel, unbeliever(-ing).
The KJV translates Strong's G571 in the following manner: that believe not (6x), unbelieving (5x), faithless (4x), unbeliever (4x), infidel (2x), thing incredible (1x), which believe not (1x).
unfaithful, faithless, (not to be trusted, perfidious)
incredible
of things
unbelieving, incredulous
without trust (in God)
Strong's Number G571 matches the Greek ἄπιστος (apistos),
which occurs 23 times in 21 verses
in the TR Greek.