- nebula⇄nebula, noun, pl.-lae,-las.
1. a mass of dust particles and gases or a cloudlike cluster of stars which occurs in interstellar space, very far away from our sun and its planets. A nebula may be either luminous or dark in appearance. Galactic nebulae - nebula⇄spiral galaxy ornebula
a galaxy or nebula appearing as one or more spiraling streams issuing from a center.
Ex. Our Milky Way system seems to be a spiral galaxy, presumably very much resembling in outline and appearance the Great Spiral in And