ἀτέρμων
From LSJ
οὗτος μὲν ὁ πιθανώτερος τῶν λόγων εἴρηται, δεῖ δὲ καὶ τὸν ἧσσον πιθανόν, ἐπεί γε δὴ λέγεται, ῥηθῆναι → this is the most credible of the stories told; but I must relate the less credible tale also, since they tell it
English (LSJ)
ον, gen. ονος,
A without bound or end, αἰών Arist.Mu.401a16; ὕπνος Mosch.3.104; ἐνόπτρων ἀ. αὐγαί the mirror's countless rays, E.Hec.926; ἀ. πέπλος having no end or issue, inextricable, A.Eu.634.