/ Dictionary / Index R radiosodium: Meaning and Definition of Find definitions for: ra•di•o•so•di•um Pronunciation: (rā"dē-ō-sō'dē-um), [key] — n. Chem. the radioactive isotope of sodium having an atomic mass of 24 and a half-life of 14.9 hours: used as a tracer in biochemistry. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radio shack radiosonde Related Content Daily Word Quiz: pristine Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language