/ Dictionary / Index R radioisotope: Meaning and Definition of Find definitions for: ra•di•o•i•so•tope Pronunciation: (rā"dē-ō-ī'su-tōp"), [key] — n. a radioactive isotope, usually artificially produced: used in physical and biological research, therapeutics, etc. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: radioisotope (Thesaurus) radioiron radio knife 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