The list is quite large but here are a few to start off with. Enjoy the dang blasted it's all over the place!
Glossary of music terms
Accent: An unusual manner of pronunciation, e.g. "Y'all sang that real good!"
Accidentals: Wrong notes
Ad Libitum: A premiere.
Agitato: A string player's state of mind when a peg slips in the middle of a piece.
Agnus dei: A famous female church composer.
Allegro: Leg fertilizer.
Altered Chord: A sonority that has been spayed.
Atonality: Disease that many modern composers suffer from. The most prominent symptom is the patient's lacking ability to make decisions.
Augmented fifth: A 36-ounce bottle.
Bar Line: A gathering of people, usually among which may be found a musician or two.
Beat: What music students to do each other with their musical instruments. The down beat is performed on the top of the head, while the up beat is struck under the chin.
Bravo: Literally, "How bold!" or "What nerve!" This is a spontaneous expression of appreciation on the part of the concertgoer after a particularly trying performance.
Breve: The way a sustained note sounds when a violinist runs out of bow.
Broken consort: When somebody in the ensemble has to leave and go to the restroom.
Cadence: When everybody hopes you're going to stop, but you don't.
Cadenza: The heroine in Monteverdi's opera "Frottola".
Cantus firmus: The part you get when you can only play four notes.
Chansons de geste: Dirty songs.
Chord: Usually spelled with an "s" on the end, means a particular type of pants, e.g. "He wears chords."
Chromatic Scale: An instrument for weighing that indicates half-pounds.