/ Dictionary / Index T tritium: Meaning and Definition of Find definitions for: trit•i•um Pronunciation: (trit'ē-um, trish'-, trish'um), [key] — n. Chem. an isotope of hydrogen having an atomic weight of three. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: tritium (Thesaurus) triticale tritoma Related Content Daily Word Quiz: cygnet Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language