Definition and background:
A medieval herald's trumpet, usually between 1 - 2 meters long, and made of brass or silver. It had a cylindrical or slightly conical bore.
A term used in the late middle ages for a large horn or trumpet
For more information on the music term "Buisine" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary