/ Dictionary / Index H heavy hydrogen: Meaning and Definition of Find definitions for: heav'y hy'drogen Pronunciation: [key] either of the heavy isotopes of hydrogen, esp. deuterium. deuterium. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heavy hitter heavy-laden Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language