The Collaborative International Dictionary of English v.0.48:

Subnuvolar \Sub*nu"vo*lar\, a. [Pref. sub + It. nuvola cloud:
   cf. L. subnubilus somewhat cloudy.]
   Under the clouds; attended or partly covered or obscured by
   clouds; somewhat cloudy. [R. & Poetic]
   [1913 Webster]

         Subnuvolar lights of evening sharply slant. --Milnes.
   [1913 Webster]