Lewis & Short

Thesprōti, ōrum, m., = Θεσπρωτοί, a people in the south-western part of Epirus, Luc. 3, 179; Liv. 43, 21, 4.
Their land was called Thesprōtĭa, ae, f., = Θεσπρωτία, Plin. 4, 1, 1, § 4; Cic. Att. 6, 3, 2.
Hence,

  1. A. Thesprōtĭus, a, um, adj., Thesprotian: sinus, Liv. 8, 24: arva, Sil. 15, 297.
  2. B. Thesprōtis, ĭdis, adj. f., Thesprotian: terra, i. e. Thesprotia, Avien. Arat. 384.