Lewis & Short

Parnāsus and -os, also Parnas-sus or -os, i, m., = Παρνασός, afterwards Παρνασσός, a high mountain in Phocis with two peaks, sacred to Apollo and the Muses, at whose foot was the city of Delphi and the Castalian spring, now range of Liakhoura, Mel. 2, 3, 4; Plin. 4, 3, 4, § 7: mons ibi verticibus petit arduus astra duobus, Nomine Parnasus, Ov. M. 1, 317: biceps, id. ib. 2, 221; Pers. prol. 2: uterque, Stat. Th. 7, 346: Parnasi deserta per ardua, Verg. G. 3, 291: Parnasus gemino petit aethera colle, Luc. 5, 72.
Hence,

  1. A. Parnāsēus (Parnass-), a, um, adj., Parnassian: Phoebus, Avien. Arat. 619.
  2. B. Parnāsis (Parnass-), ĭdis, f. adj., Parnassian: lauro Parnaside vinctus, Ov. M. 11, 165.
  3. C. Parnāsĭus (Parnass-), a, um, adj., Parnassian: rupes, Verg. E. 6, 29: laurus, id. G. 2, 18: templa, of Apollo, Ov. M. 5, 278: Themis, so called because she possessed the Delphic oracle before Apollo, id. ib. 4, 642: vox, the Delphic oracle, Val. Fl. 3, 618: tu, precor, ignarum doceas, Parnasia, vatem, O muse! Claud. Cons. Prob. et Olybr. 71.