What does Ias mean in Latin?

Ias, a proper noun, means “Ionic Greek (dialect of Ancient Greek)”.

What is the genitive of Ias?

The genitive singular is Iadis. Ias is feminine, third declension.

In classical Latin, [ˈi.as]; in ecclesiastical (church) Latin, [ˈiː.as].

proper noun · femininethird declension

Ias f sg (genitive Iadis)

Classical[ˈi.as]Ecclesiastical[ˈiː.as]

Late LatinfemininesingularIonic Greek (dialect of Ancient Greek)
Quinque sunt linguae Graecorum, Ias Doris Atthis Aeolis coene. iuxta has igitur quinque linguas et Latina verba conprehensa colliguntur hoc modo. Ias relictis propriis utitur similibus quasi propriis nominibus ac versatur in omnibus tropis.late 4th century CE, Diomedes Grammaticus, Artis Grammaticae libri III 440.5–8

From Ancient Greek Ἰ̆ά̆ς (Ĭá̆s, “Ionian, Ionic”, as a noun “an Ionian woman, the Ionic dialect”, feminine adjective).