Lewis & Short

nūbĭlo, v. a. and n. [nubilum], to be cloudy or overcast; to make cloudy, to overcast.

  1. I. Lit.: si nubilare coeperit, Varr. R. R. 1, 13, 5.
          1. (β) Impers. pass.: ubi nubilabitur, Cato, R. R. 88, 2.
    1. B. Transf., to be cloudy, dull: nubilans fulgor carbunculi, Plin. 37, 7, 25, § 94.
  2. II. Trop., to cloud over, to obscure (post-class.): lucem dei, Paul. Nol. Carm. 10, 37.