1. slang An informal shortening of "shotgun." I knew I should have brought a shotty with me to this job. The best guns to wield in the game are double shotties. You can really tear through your opponents with them!
2. slang An informal shortening of "shotgun," meaning "riding in the front passenger seat of a car," or used as an interjection to claim that privilege. An allusion to the passenger seat of horse-drawn carriages being occupied by someone carrying a shotgun in order to protect the carriage's contents or occupants. You rode shotty last time—it's my turn! The first one to shout "Shotty!" gets to ride in the front seat. That's always been the rule!
n. the seat in a car behind the shotgun or passenger seat. (see also ride shotgun for an explanation.) I wanna ride shotty back!