Lewis & Short

Massăgĕtae, ārum, m., = Μασσαγέται, a Scythian people, to the east of the Caspian Sea, in the mod. Sangaria and Mongolia, Mel. 1, 2, 5; Plin. 6, 17, 19, § 50; Nep. Reg. 1, 2; Stat. Achill. 1, 307: retusum in Massagetas Arabasque ferrum, Hor. C. 1, 35, 40.
In sing. collect.: Massăgĕtes, ae, m., one of the Massagetæ, Luc. 3, 283: Massageten monstrans, Sil. 3, 360; Claud. ap. Ruf. 1, 312.