Lewis & Short

Būthrōtum, i, n. (Būthrōtŏs, i, f., Ov. M. 13, 721), = Βουθρωτόν and Βουθρωτός, a town on the coast of Epirus, now Butrinto, Caes. B. C. 3, 16; Verg. A. 3, 293 sq.; Mel. 2, 3, 10; Plin. 4, 1, 1, § 4.
Hence, Būthrōtĭus, a, um, adj., of Buthrotum: ager, causa, Cic. Att. 16, 16, A, 4: Plancus, id. ib. 15, 29, 3; and subst.: Būthrōtĭi, ōrum, m., the inhabitants of Buthrotum, id. ib. 14, 11, 2; 15, 2, 2; 16, 16, A, 4.