[1] : The Collaborative International Dictionary of English v.0.48

nebula \neb"ula\ ne^b"-ul.a, n.; pl. nebulae
   ne^b"-ul=e. l., mist, cloud; akin to gr. nefe`lh,
   ne`fos, cloud, mist, g. nebel mist, ohg. nebul, d. nevel,
   skr. nabhas cloud, mist. cf. nebule.
   1. astron. a faint, cloudlike, self-luminous mass of matter
      situated beyond the solar system among the stars. the term
      was originally applied to any diffuse luminous region.
      now, technically, it is applied to interstellar clouds of
      dust and gases diffuse nebula. however distant
      galaxies and very distant star clusters often appear like
      them in the telescope, such as the spiral nebula in
      andromeda, known now to be a distant galaxy.
      1913 webster +pjc

   2. med.
      a a white spot or a slight opacity of the cornea.
      b a cloudy appearance in the urine. obs.
          1913 webster
see also:
nebulae nebule diffuse nebula spiral nebula 

[2] : WordNet (r) 2.0

nebula
     n 1: a medicinal liquid preparation intended for use in an
          atomizer
     2: cloudiness of the urine
     3: an immense cloud of gas mainly hydrogen and dust in
        interstellar space
     4: pathology a faint cloudy spot on the cornea
     also: nebulae pl
see also:
nebulae 

[3] : WordNet (r) 2.0

nebulae
     see nebula
see also:
nebula 

Nebulae >> N Words
Nebulae, definition of term: Nebulae
nebulae_pag1.html