/ Dictionary / Index E emission nebula: Meaning and Definition of Find definitions for: emis'sion neb"ula Pronunciation: [key] — Astron. Astron. a bright diffuse nebula that emits light as a result of ionization of its gas atoms by ultraviolet radiation, as the Orion Nebula, planetary nebulae, and supernova remnants, as the Crab Nebula. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. emission emission spectrum Related Content Daily Word Quiz: drowsy Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language