| Nebula 1. (n.) A faint, cloudlike, mass of interstellar dust or gas. True nebulae are gaseous; but very distant star clusters often appear like them in the telescope. 2. (n.) A white spot or a slight opacity of the cornea. 3. (n.) A cloudy appearance in the urine. Thesaurus Entries Black Magellanic Cloud, Crab Nebula, Gegenschein, bright diffuse nebula, coalsack, counterglow, dark cloud, dark nebula, diffuse nebula, dust cloud, gaseous nebula, nebula of Lyra, nebular hypothesis, nebulosity, nebulous stars, planetary nebula, ring nebula, the Coalsack, zodiacal light |