Liddel and Scott Greek Lexicon

ἀάατος, ον, (ἀάω) in Il. ^__^, not to be injured, inviolable, νῦν μοι ὄμθσσον ἀ. Στυγὸς ὕδωρ 14.271.

II in Od. ^_^^, ἄεθλος ἀ. ἐκτετέλεσται 22.5, cf. 21.9, prob. unimpeachable, i.e. decisive.

III later, invincible, κάρτος ἀάᾰτος A.R. 2.77. (ἀάfατος, cf. sq., Hsch. )