/ Dictionary / Index R radio source: Meaning and Definition of Find definitions for: ra'dio source" Pronunciation: [key] — Astron. Astron. a cosmic object or phenomenon, as a galaxy, pulsar, quasar, or the remnant of a supernova or of a galactic collision, that emits radio waves. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiosonde radio spectrum Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language