/ Dictionary / Index H heavy nitrogen: Meaning and Definition of Find definitions for: heav'y ni'trogen Pronunciation: [key] the stable isotope of nitrogen having a mass number of 15. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heavy mineral oil heavy oxygen Related Content Daily Word Quiz: impetuous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language