Lewis & Short

Rhamnūs, untis, f., = Ῥαμνοῦς, the northernmost town of Attica, famed for an ancient temple of Themis, and in later times for a statue of Nemesis, the mod. Ovriokastro, Plin. 4, 7, 11, § 24; 36, 5, 4, § 17; Luc. 5, 233.
Hence,

    1. 1. Rhamnūsĭus, a, um, adj., Rhamnusian Rhamnusium se aiebat esse, from Rhamnus, Ter. And. 5, 4, 27: Antiphon, Cic. Brut. 12, 47: virgo, i. e. Nemesis, Cat. 66, 71; also called dea, Claud. B. Get. 631; and simply Rhamnūsia, ae, f., Ov. M. 3, 406; id. Tr. 5, 8, 9; Stat S. 3, 5, 5.
    2. 2. Rhamnūsis, ĭdis, f., the Rhamnusian goddess, i. e. Nemesis, Ov. M. 14, 694.