Source : Webster's Revised Unabridged Dictionary (1913)

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

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

Source : WordNet®

nebulous
     adj 1: lacking definite form or limits; "gropes among cloudy issues
            toward a feeble conclusion"- H.T.Moore; "nebulous
            distinction between pride and conceit" [syn: {cloudy},
             {nebulose}]
     2: lacking definition or definite content; "nebulous reasons";
        "unfixed as were her general notions of what men ought to
        be"- Jane Austen [syn: {unfixed}]