/ Dictionary / Index R radiation therapy: Meaning and Definition of Find definitions for: radia'tion ther"apy Pronunciation: [key] radiotherapy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiation sickness radiative Related Content Daily Word Quiz: portent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language