/ Dictionary / Index E euphonium: Meaning and Definition of Find definitions for: eu•pho•ni•um Pronunciation: (y-fō'nē-um), [key] — n. a brass musical instrument similar to the baritone tuba but somewhat smaller, with a wider bore and mellower tone, and often having a second bell. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: euphonium (Thesaurus) euphonious euphonize Related Content Daily Word Quiz: mamba Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language