Definition and background:
The most common range of male voice pitched between the tenor and bass. Usually a baritone has a range of the low G in the bass clef to an F above the bass clef. The term baritone is also applied to instruments of a lower range such as the baritone horn or baritone saxophon.(1) Male voice between bass and tenor. (2) Wind instrument in the baritone range.
The baritone saxhorn, member of the saxhorn family in 8-ft C or 9-ft B-flat with narrower bore than the bass saxhorn of the same pitch (euphonium). In the U.S.A. the term is often used interchangeably with Euphonium
For more information on the music term "Baritone" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary