Lewis & Short

Trīnā̆crĭa, ae, f., = Τρινακρία (with three promontories), the island of Sicily, Verg. A. 3, 440; 3, 582; Ov. P. 4, 15, 15; id. M. 5, 476; Just. 4, 2, 1.
Hence,

  1. A. Trīnā̆-crĭus, a, um, adj., Trinacrian, Sicitian: Pachynus, Verg. A. 3, 429: Aetna, id. ib. 3, 554; also called Trinacria rupes, Cat. 68, 53: mare, Ov. F. 4, 287: unda, Verg. A. 3, 384: litus, id. ib. 1, 196: viri, id. ib. 5, 530: pubes, id. ib. 5, 450: equi, id. ib. 5, 573.
  2. B. Trīnā̆cris, ĭdis, adj. f., Trinacrian, Sicilian: terra, i. e. Trinacria or Sicily, Ov. F. 4, 420; also called Trinacris insula, id. M. 5, 347: Hybla, id. Tr. 5, 13, 22.
    Subst.: Trīnăcris (sc. insula), the island of Trinacria, Sicily, Ov. P. 2, 10, 22.