/ Dictionary / Index R radionuclide: Meaning and Definition of Find definitions for: ra•di•o•nu•clide Pronunciation: (rā"dē-ō-n'klīd, -ny'-), [key] — n. Physics. a radioactive nuclide. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiomicrometer radiopaque Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language