Lewis & Short

dīrus, a, um, adj. [Sanscr. root dī, to flee; Gr. δέος, δείδω, δεινός], fearful, awful (for syn. cf.: saevus, atrox, ferox, crudelis, trux, furens, furiosus, immitis).

  1. I. Orig. belonging to the lang. of augurs; of fate, ill-omened, ominous, boding, portentous: QVAE AVGVR INIVSTA, NEFASTA VITIOSA DIRA DEFIXERIT, IRRITA INFECTAQVE SVNTO, Cic. Leg. 2, 8 fin.; cf. id. Div. 1, 16: tristissima exta sine capite fuerunt, quibus nihil videtur esse dirius, id. ib. 2, 15 fin.; cf.: bubo, dirum mortalibus omen, Ov. M. 5, 550: omen, Tac. H. 3, 56; Suet. Aug. 92; id. Tib. 1, 3, 17: aves, Tac. A. 12, 43; Suet. Claud. 22: alites, Plin. 18, 1, 1, § 4: somnia, Val. Fl. 3, 59: tempus, Cic. Poët. Div. 1, 11, 18: exsecrationes, Liv. 40, 56; 28, 22; Suet. Claud. 12; cf. deprecationes, Plin. 28, 2, 4, § 19: detestatio, Hor. Epod. 5, 89: ritus sacrorum, Tac. A. 16, 8: religio loci, Verg. A. 8, 350 et saep.
    Hence, as subst.:
      1. 1. dīrae, ārum, f.
          1. (α) (sc. res), ill-boding things, portents, unlucky signs: dirarum obnuntiatio, id. ib.; Plin. 28, 2, 4, § 17; 28, 2, 5, § 26; Tac. A. 6, 24 al.; Hor. Epod. 5, 89; Müll. Etrusk. 2, p. 117.
          2. (β) As a nom. propr., Dīrae, the Furies, Verg. A. 12, 845 sq.; 4, 473; Val. Fl. 1, 804; Aur. Vict. Epit. 21 al.; called also Dirae deae, sorores, Verg. A. 7, 324 and 454.
      2. 2. dīra, ōrum, n., fearful things, ill-boding events: in dira et in vitiosa incurrimus, Cic. Div. 1, 16, 29; id. Leg. 2, 8, 21; cf.: me mihi dira precari cogis, to curse, invoke curses on, Tib. 2, 6, 17: dira passus, Vulg. Sirach, 38, 16.
  2. II. Transf., of character, dreadful, horrible, terrible, abominable, detestable (so almost exclusively poet.; a very favorite expression with the Aug. poets; in the Ciceron. per. not at all; but cf. diritas, II.): senex dirissimus, Varr. Poët. ap. Non. 100, 30: Dea, i. e. Circe, Ov. M. 14, 278: Ulixes, Verg. A. 2, 261; 762: Hannibal, Hor. C. 2, 12, 2 al.: durum, id. ib. 3, 6, 36 (also ap. Quint. 8, 2, 9): Afer, Hor. C. 4, 4, 42: Amulius, Ov. F. 4, 53: noverca, id. H. 12, 188: pellex, id. ib. 5, 60 et saep.: hydra, Hor. Ep. 2, 1, 10: serpens, Ov. M. 2, 651: victima, id. A. A. 1, 334: parens, fell, cruel, id. ib. 2, 383: soror, Stat. S. 5, 3, 84: parentes, Manil. 5, 541.
        1. b. Of inanimate and abstr. subjects: regio, Ov. Tr. 3, 3, 5: facies, id. F. 1, 553: dapes, id. ib. 6, 663: venena, Hor. Epod. 5, 61; id. S. 1, 9, 31: Asphaltites lacus, Plin. 5, 15, 15, § 71: scopulus, id. 4, 11, 18, § 51: duarum Syrtium vadoso mari diri sinus, id. 5, 4, 4, § 26 et saep.: bellum, Verg. A. 11, 217: nefas, id. ib. 4, 563: sollicitudines, Hor. Epod. 13, 10: amores, Ov. M. 10, 426: superbia, id. ib. 3, 354: quies, Tac. A. 1, 65 et saep.
          Poet., answering to the Gr. δεινός, with inf.: dira portas quassare trabs, Sil. 4, 284.
    1. B. Skilful: in complicandis negotiis, Amm. 14, 5, 8.