ἀδιάσφαλτος
From LSJ
Τὰς γὰρ ἡδονὰς ὅταν προδῶσιν ἄνδρες, οὐ τίθημ' ἐγὼ ζῆν τοῦτον, ἀλλ' ἔμψυχον ἡγοῦμαι νεκρόν → But when people lose their pleasures, I do not consider this life – rather, it is just a corpse with a soul
English (LSJ)
ον, A free from error, μέθοδοι Hero *Geep.164. Adv. -τως Ps.-Dioph.p.xxi H.
Spanish (DGE)
-ον infalible μέθοδον Hero Lib.Geep.164.