/ Dictionary / Index R radiotracer: Meaning and Definition of Find definitions for: ra•di•o•trac•er Pronunciation: (rā'dē-ō-trā"sur), [key] — n. Chem. a radioactive isotope used as a tracer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiotoxic radiotransparent Related Content Daily Word Quiz: morose Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language