Lewis & Short

Trans-dānŭbĭānus (-dānŭvĭā-nus), a, um, adj. [Danubius], situated beyond the Danube, Transdanubian: Dacia, Vop. Aur. 39, 7: regio, Liv. 40, 58, 8 (dub.; al. Aquiloniam regionem).
In plur. subst.:Transdānŭbĭāni, ōrum, m., the nations beyond the Danube, Inscr. Orell. 750.