/ Dictionary / Index H heavy oxygen: Meaning and Definition of Find definitions for: heav'y ox'ygen Pronunciation: [key] either of the two stable isotopes of oxygen having mass numbers of 17 and 18. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heavy nitrogen heavyset 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