Lewis & Short

rŭdo (rūdo, Pers. 3, 9), īvi, ītum (gen. plur. part. rudentūm, Verg. A. 7, 16), 3, v. n. and a. [Sanscr. root ru-, to howl; Gr. ὠρύω; cf. Lat.: ravis, ravus, raucus], to roar, bellow, bray.

  1. I. Lit., of animals; e. g. of lions, Verg. A. 7, 16; of stags, id. G. 3, 374; of bears, Claud. Cons. Mall. Theod. 298; esp. freq. of the braying of an ass, Ov. A. A. 3, 290; id. F. 1, 433; 6, 342; Pers. 3, 9.
  2. II. Transf., of men, to roar or cry out: haec inquam rudet ex rostris, Lucil. ap. Varr. L. L. 7, § 103 Müll.: (Cacum) insueta rudentem Alcides telis premit, Verg. A. 8, 248.
    Of things: rudentem proram, creaking, groaning, Verg. A. 3, 561.