Lewis & Short

unda, ae, f. [Sanscr. root ud-, und-, to be wet; whence, uda, water; Angl. -Sax. ydhu, wave; Slav. voda, water; Gr. ὕδωρ, ὑάδες; Goth. vatō, water], a wave, billow, surge (syn. fluctus).

  1. I. Lit.: mare plenum undarum, Plaut. Mil. 2, 6, 33: unda, cum est pulsa remis, purpurascit, Cic. Fragm. ap. Non. 162, 30: via, quae fert Acherontis ad undas, Verg. A. 6, 295; Lucr. 1, 374; 1, 380; 3, 494; Hor. C. 1, 12, 32; 4, 14, 20; id. Ep. 2, 2, 176; Ov. M. 1, 570.
    Collect.: prora remissa subito navem undae adfligebat, Liv. 24, 34, 11.
    1. B. Transf.
      1. 1. In gen.
        1. a. Water, moisture (mostly poet.; cf.: aqua, lympha): (Proteus) flumen eras, interdum undis contrarius ignis, Ov. M. 8, 737: fontis in undā, id. ib. 4, 98; cf.: fons tenui perlucidus undā, id. ib. 3, 161: (Noti) canis fluit unda capillis, id. ib. 1, 266: nivales, snow-water, Mart. 14, 118, 1: ignem Pollux undamque jugalem Praetulit, fire and water, as symbols of housekeeping, Val. Fl. 8, 245, hence, faciunt justos ignis et unda viros, i. e. real, proper husbands, Ov. A. A. 2, 598.
        2. b. A fluid, liquid. manans naribus unda Sangninis, Sil. 10, 245: preli, i. e. oil, Plin. 15, 1, 2, § 5: croci, Mart. 8, 33. 4; 13, 40, 1.
          Cf the lava from Ætna, Lucil. Aet. 303.
      2. 2. Of wavelike things (poet.): aëriae, i. e. the air, Lucr. 2, 152: quā plurimus undam Fumus agit, Verg. A. 8, 257.
        Of a lion’s mane, Mart. 8, 55, 10.
      3. 3. In architecture, for the Gr. cymatium (κυματίον, a little wave), a talon, ogee, Vitr. 5, 7.
  2. II. Trop., of the wavelike agitation of a multitude, etc., a surge, billow, stream, tide, = aestus: campus atque illae undae comitiorum, Cic. Planc. 6, 15: nunc agilis fio et mersor civilibus undis, Hor. Ep. 1, 1, 16: adversis rerum immersabilis undis, id. ib. 1, 2, 22: curarum, Cat. 64, 62: bellorum, Claud. in Eutr. 2, 507: salutantūm unda, a stream, crowd, throng, Verg. G. 2, 462; so, undae Boiorum, Sil. 4, 159.