ἀδιά-πτωτος · adia-ptōtos — LSJ
infallible, Hp. Decent. 12, S.E. M. 7.110; ἀρχὴ ἀ. τῇ πόλει PRyl. 77.46 (ii A.D.). Adv. -τως Plb. 6.26.4, cf. Stoic. 3.69; unerringly, of archers, Hld. 9.18.
faultless, of writers, Longin. 33.5; τὸ ἀ. perfection of style, Id. 36.4; φράσις Diog.Bab.Stoic. 3.214; προφορά D.T. 629.12.
Gramm., not using cases at random, A.D. Pron. 109.23.
uninflected, EM 643.47.