Lewis & Short

Perrhaebi, ōrum, m., = Περραιβοί, a people of Thessaly about Tempe and Mount Olympus, the Perrhœbians, Liv. 33, 32; 34; 42, 53.
Hence,

  1. A. Perrhaebus, a, um, adj., Perrhœbian, Thessalian: Pindus, Prop. 3, 3 (4, 4), 33, 55: Caeneus, Ov. M. 12, 172.
  2. B. Perrhaebĭa, ae, f., = Περραιβία, the country of the Perrhœbians, Perrhœbia, Cic. Pis. 40, 96; Liv. 31, 41, 5.