Lewis Short
(verb) : nūbĭlo, and n. nubilum
* To be cloudy or overcast; to make cloudy, to overcast.
* Lit.: si nubilare coeperit,Varr. R. R. 1, 13, 5.
* Impers. pass.: ubi nubilabitur,Cato, R. R. 88, 2.
* Trop., to cloud over, to obscure (post-class.): lucem dei,Paul. Nol. Carm. 10, 37.
Charlton T. Lewis, Charles Short, A Latin Dictionary