Lewis & Short

nī̆gro, āvi, ātum, 1, v. n. and a. [id.].

  1. I. Neutr., to be black: ea, quae nigrant nigro de semine nata, Lucr. 2, 733.
  2. II. Act., to make black, to blacken.
    1. A. Lit.: mgrāsset sibi planctu lacertos, Stat. S. 2, 6, 83.
    2. B. Trop., to make dark, to darken: nigrati ignorantiae tenebris, Tert. adv. Marc. 4, 8.
      Hence, nī̆grans, antis, P. a., black, dark-colored, dusky: nigrantia boum cornua, Varr R. R. 2, 5: nigrantes terga juvenci, Verg. A. 5, 97: nigrantes alae, Ov. M. 2, 535: nigrantes domos ammarum intrāsse silentūm, Prop. 3, 12, 33 (4, 11, 33): nigrante profundo, the sea, Sil. 17, 258: litora, Val. Fl. 4, 697: aegis, i. e. that produces clouds, Verg. A. 8, 353.