ἄπταιστος
From LSJ
κοινὸν τύχη, γνώμη δὲ τῶν κεκτημένων → good luck is anyone's, judgment belongs only to those who possess it
English (LSJ)
ον,
A not stumbling, ἀπταιστστερον παρέχειν τὸν ἵππον make a horse less aptto stumble, X.Eq.1.6: metaph., ἄ ἐν τῷ βίῳ Epict. Gnom.52; δώμασιν ἀ. Limen.43, cf.M.Ant.5.9; βίος Luc.Am.46; infallible, Plot.5.3.17, Alex.Aphr.in Metaph.713.12; ἀλήθεια Iamb.Myst. 3.31; θεοὶ διδασκάλων-ότατοι Max.Tyr.38.1. Adv. -τως Pl.Tht.144b; inevitably, Gal.14.230: Comp.-ότερον with greater precision, Ptol.Tetr. 177:—also ἀπρο-τί, Hdn.Epim.256. 2 intact, Plu.2.691d. II not causing to stumble, giving a good footing, λεία καὶ ἄ. ὁδός Max. Tyr.5.2.