Lewis Short
(verb) : nīgro, āvi, ātum, 1, and
* A. [id.].
* Neutr., to be black: ea, quae nigrant nigro de semine nata,Lucr. 2, 733.
* Act., to make black, to blacken.
* Lit.: mgrāsset sibi planctu lacertos,Stat. S. 2, 6, 83.
* Trop., to make dark, to darken: nigrati ignorantiae tenebris,Tert. adv. Marc. 4, 8.—Hence, nīgrans, 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.
Charlton T. Lewis, Charles Short, A Latin Dictionary