The Collaborative International Dictionary of English v.0.48:

Nebulous \Neb"u*lous\, a. [L. nebulosus: cf. F. n['e]buleux. See
   Nebula.]
   1. Cloudy; hazy; misty.
      [1913 Webster]

   2. (Astron.) Of, pertaining to, or having the appearance of,
      a nebula; nebular; cloudlike.
      [1913 Webster] -- Neb"u*lous*ly, adv. --
      Neb"u*lous*ness, n.
      [1913 Webster]