/ Dictionary / Index C chromium 51: Meaning and Definition of Find definitions for: chromium 51 Pronunciation: [key] the radioactive isotope of chromium having a mass number 51 and a half-life of 27.8 days: used as a tracer. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. chromium chromium acetate Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language