ἀκαταγώνιστος
From LSJ
Ὅσον ζῇς, φαίνου, μηδὲν ὅλως σὺ λυποῦ· πρὸς ὀλίγον ἐστὶ τὸ ζῆν, τὸ τέλος ὁ χρόνος ἀπαιτεῖ. → While you live, shine; have no grief at all; life exists only for a short while, and time demands its toll.
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.