ἀκαταγώνιστος
From LSJ
ὤμοι, πέπληγμαι καιρίαν πληγὴν ἔσω → Alas! I am struck deep with a mortal blow! | Ah me! I am struck—a right-aimed stroke within me (Aeschylus, Agamemnon 1343)
English (LSJ)
ον,
A unconquerable, D.S.17.26, Olymp. Hist.p.451 D., Procl. in Cra. p.112P.; epith. of the Stoic sage, Stoic.1.53.
Greek (Liddell-Scott)
ἀκαταγώνιστος: -ον, ἀκατανίκητος, Διόδ. 17. 26.