1. The act of receiving a "big one" while playing a trombone (or small one, depending on the person).
2. Getting a "big one" that resembles the shape of a trombone.
3. Getting a "big one" when catching the eye of a particularly attractive or sexy band player who just happens to play the trombone.
Dude 1: Oh crap, man! I just got a tromboner!
Dude 2: Hide it quickly! People might see it's distinct shape!
Dude 1: Man, he/she just gave me a tromboner!
Dude 2: Don't hide it, it's a symbol of pride!