UNERRING
inerrable, inerrant, unerring
(adjective) not liable to error; “the Church was...theoretically inerrant and omnicompetent”-G.G.Coulton; “lack an inerrant literary sense”; “an unerring marksman”
Source: WordNet® 3.1
Etymology
Adjective
unerring (not comparable)
(often, figurative) consistently accurate; not missing a target.
Source: Wiktionary
Un*err"ing, a.
Definition: Committing no mistake; incapable or error or failure certain;
sure; unfailing; as, the unerring wisdom of God.
Hissing in air the unerring weapon flew. Dryden.
Source: Webster’s Unabridged Dictionary 1913 Edition