Lewis & Short

rūpes, is (collat. form rūpa, ae, App. M. 6, p. 72 Hildebr. min.; cf. Gloss. Isid. p. 693),f. [rumpo], a rock: ex magnis rupibus nactus planitiem, Caes. B. C. 1, 70: cum (oppidum) ex omnibus in circuitu partibus altissimas rupes despectusque haberet, id. B. G. 2, 29; cf. Liv. 32, 4; and with this cf.: inter saxa rupesque, id. 21, 40: ex rupe Tarpeiā, id. 7, 10: Parnasia, Verg. E. 6, 29: aëria, id. G. 4, 508: ardua, Ov. F. 5, 293; id. P. 1, 8, 51: cavae, caverns, grottos, Verg. G. 3, 253; so, ima (Sibyllae), id. A. 3, 443.
Of a cliff, Verg. A. 10, 693; Luc. 5, 514; Val. Fl. 3, 108; 4, 637; cf.: personantibus et respondentibus inter se rupibus, Just. 24, 6, 8.