Lewis & Short

somnĭum, ii, n. [somnus].

  1. I. Lit., a dream, Cic. Div. 1, 20, 39; 2, 58, 119; Plin. 10, 75, 98, § 211; Macr. Somn. Scip. 1, 3; Lact. Opif. Dei, 18: rex Priamus somnio perculsus, Enn. ap. Cic. Div. 1, 21, 42 (Trag. v. 59 Vahl.): dum huic conicio somnium, interpret, Plaut. Curc. 2, 2, 3; cf. id. Rud. 3, 1, 19: interpretes somniorum, Cic. Div. 1, 58, 132: jucundissima somnia, id. Fin. 5, 20, 55: per somnia loquentes, talking in their sleep, Lucr. 5, 1158; cf.: quae somnio visa fuerant, Liv. 8, 6, 11 Weissenb.
    1. B. Personified: Somnia, dreams, as divinities, Cic. N. D. 3, 17, 44; Ov. M. 11, 588; 11, 614 sq
  2. II. Transf.
    1. A. For any thing idle, silly, or without foundation (cf. somnio, II.), a dream, an idle whim or fancy, stuff, nonsense: tu, quantus quantus, nihil nisi sapientia es: Ille somnium, Ter. Ad. 3, 3, 41: de argento, somnium, id. ib. 2, 1, 50; id. Phorm. 5, 6, 34.
      Plur.: fabulae! … logi! … somnia! Ter. Phorm. 3, 2, 9: et vigilans stertis nec somnia cernere cessas, visions, Lucr. 3, 1048; cf. id. 1, 105: spes inanes et velut somnia quaedam vigilantium, Quint. 6, 2, 30: exposui fere non philosophorum judicia, sed delirantium somnia, Cic. N. D. 1, 16, 42: Chrysippus Stoicorum somniorum vaferrimus interpres, id. ib. 1, 15, 39: leviter curare videtur, Quo promissa cadant et somnia Pythagorea, Hor. Ep. 2, 1, 52.
    2. B. Poet.: Somnus, tibi somnia tristia portans, i. e. fatal sleep, Verg. A. 5, 840.