/ Dictionary / Index R radio spectrum: Meaning and Definition of Find definitions for: ra'dio spec"trum Pronunciation: [key] the portion of the electromagnetic spectrum that includes radio waves. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radio source radio star 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