Lewis Short
(adjective) : Căystrŏs or -us, i, m., = Κάϋστρος
* A river in Lydia, which rises in Mount Tmolus, and falls into the sea at Ephesus, celebrated for the great number of its swans, now Kara - Su: Caystros,Ov. M. 5, 386; Mel. 1, 17, 2: Caystrus,Sen. Q. N. 4, 2, 19; Verg. G. 1, 384; Prop. 3 (4), 22, 15; Ov. M. 2, 253; Plin. 5, 29, 31, § 115.—Hence, Căy-strĭus, a, um, , of Caystros: ales = cygnus,Ov. Tr. 5, 1, 11.
Charlton T. Lewis, Charles Short, A Latin Dictionary