ἄτρεστος
From LSJ
τῶν Λειβηθρίων ἀμουσότερος → more uncultured than Leibethrans, more uncultured than the people of Leibethra, lowest degree of mental cultivation
English (LSJ)
ον, (τρέω)
A not trembling, fearless, Trag., and Pl.Cra.395c: c. gen., ἄ. μάχας fearless of fight, A.Pr.416 (lyr.); ἄ. ἐν μάχαις S.Aj. 365 (lyr.); ἄ. εὕδειν securely, Id.OT586. Adv. -τως A.Supp.240: neut. pl. ἄτρεστα as Adv., E.Ion1198.
German (Pape)
[Seite 388] nicht zitternd, unerschrocken, bes. Tragg., καρδία Aesch. Ag. 1375; μάχης Prom. 414; ἐν μάχαις Soph. Ai. 358; σὺν φόβοις entggstzt O. R. 586; ἄτρεστα adverbial Eur. Ion. 1198; so sp. D.; auch Plat. Crat. 395 b.