Origin: L, mist, cloud; akin to Gr, cloud, mist, G. Nebel mist, OHG. Nebul, D. Nevel, Skr. Nabhas cloud, mist. Cf. Nebule.
1. (Science: astronomy) A faint, cloudlike, self–luminous mass of matter situated beyond the solar system among the stars. True nebulae are gaseous; but very distant star clusters often appear like them in the telescope.
2. (Science: medicine) A white spot or a slight opacity of the cornea. A cloudy appearance in the urine.