Lewis & Short

tĕnē̆brōsus, a, um, adj. [tenebrae], dark, gloomy (poet. and in post-Aug. prose).

  1. I. Lit.: aëra dimovit tenebrosum et dispu lit umbras, Verg. A. 5, 839: palus, id. ib. 6, 107: Tartara, Ov. M. 1, 113: sedes, id. ib. 5, 359: specus tenebroso caecus hiatu, id. ib. 7, 409: carcer, Luc. 2, 79: balnea Grylli, Mart. 1, 60, 3 (cf. id. 2, 14, 13): caeruleo tenebrosa situ, Val. Fl. 3, 400: silentia, Claud. Rapt. Pros. 2, 329.
    Comp.: carcer, Tert. Anim. 1 fin.
    Subst.:     tĕnē̆brōsum, i, n., the dark, Lact. 7, 4, 12; and plur.: in tenebrosis, Vulg. Thren. 3, 6.
  2. II. Trop.: cor, Prud. Apoth. 195: tenebrosissimus error, Cod. Just. 6, 43, 3 med.
    * Adv.: tĕ-nē̆brōsē, darkly, Hier. in Ion. 4, 6 (with occulte).