Lewis & Short

Styx, ygis and ygos, f., = Στύξ.

  1. I. A fountain in Arcadia, the icy-cold water of which caused death, Plin. 2, 103, 106, § 231; Sen. Q. N. 3, 25, 1; Vitr. 8, 3, 16; Just. 12, 14, 7; Curt. 10, 10, 17.
  2. II. In mythology, a river in the infernal regions, by which the gods swore, Cic. N. D. 3, 17, 43; Verg. G. 4, 480; Ov. M. 12, 322; id. A. A. 1, 635; Sil. 13, 570; Stat. Th. 8, 30; id. Achill. 1, 269 al.
    Hence, poet., the infernal regions, the lower world, Verg. G. 1, 243; Ov. M. 10, 13; id. P. 4, 8, 60; id. Tr. 5, 2, 74; Mart. 4, 60, 4; and for poison: miscuit undis Styga Sidoniis, Sen. Oedip. 163.
    Hence,
      1. 1. Stygĭus, a, um, adj., of or belonging to the Styx, Stygian; and poet., of or belonging to the lower world, infernal: palus, Verg. A. 6, 323: aquae, id. ib. 6, 374: torrens, Ov. M. 3, 290: cymba, i. e. of Charon, Verg. G. 4, 506; so, carina, id. A. 6, 391: Juppiter, i. e. Pluto, id. ib. 4, 638; cf. id. ib. 6, 252: frater, id. ib. 9, 104: Juno, i.e. Proserpine, Stat. Th. 4, 526: canes, Luc. 6, 733: manes, Val. Fl. 1, 730: umbrae, Ov. M. 1, 139.
        Hence, poet., deadly, fatal, pernicious, awful, etc.: vis, Verg. A. 5, 855; cf. nox, i. e. death, Ov. M. 3, 695: bubo, id. ib. 15, 791 et saep.
      2. * 2. Stygĭālis, e, adj., Stygian: sacra, Verg. Cir. 373.