[syn: nebulous, unfixed]
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]
WordNet (r) 3.0 (2006):
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, nebulous]
    2: of or relating to or resembling a nebula; "the nebular
       hypothesis of the origin of the solar system" [syn:
       nebular, nebulous]
    3: lacking definition or definite content; "nebulous reasons";
       "unfixed as were her general notions of what men ought to
       be"- Jane Austen [syn: nebulous, unfixed]
Moby Thesaurus II by Grady Ward, 1.0:
111 Moby Thesaurus words for "nebulous":
   Cynthian, abstract, amorphous, anagalactic, asteroidal, astral,
   astrologic, astrologistic, astrologous, astronomic, astrophysical,
   bland, blind, blurred, broad, castellatus, celestial,
   circumplanetary, cirrose, cirrous, cislunar, clear as mud,
   cloud-flecked, clouded, cloudy, collective, cumuliform, cumulous,
   dark, dim, dirty, empyreal, empyrean, equinoctial, extragalactic,
   faint, featureless, foggy, fuzzy, galactic, general, generalized,
   generic, gloomy, hazy, heavenly, heavy, heliacal, ill-defined,
   indefinite, indeterminate, indistinct, intercosmic, interplanetary,
   intersidereal, interstellar, lenticularis, lunar, lunary, lunate,
   lunular, lunulate, mammatus, meteoric, meteoritic, misty, muddy,
   murky, nebular, nebulose, neutral, nimbose, nonspecific, nubilous,
   obscure, opaque, overcast, overclouded, pale, planetal,
   planetarian, planetary, planetesimal, semilunar, shadowy,
   shapeless, sidereal, solar, sphery, squally, star-spangled,
   star-studded, starry, stellar, stellary, stormy, stratiform,
   stratous, terrestrial, thunderheaded, transcendent, turbid,
   uncharacterized, unclear, undifferentiated, unplain, unspecified,
   uranic, vague, wide, zodiacal