euphonium[yo̵̅o̅ fō′nē əm]
euphonium definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a valved brass instrument like the baritone but more mellow in tone, due to a larger bore
Origin: ; from Classical Greek euphōnos, musical (see euphony) plush (harmon)ium
euphonium definition by American Heritage Dictionary
A brass wind instrument similar to the tuba but having a somewhat higher pitch and a mellower sound.
Origin: From Greek euphōnos, sweet-voiced; see euphony.