A vicious, highly infectious disease in men that is spread when the groin region gets intentionally farted on by another person (not necessarily one with fartballs). Common symptoms are denial and irrational aggressiveness towards people named Michael.
Bob: Hey Michael, I heard Joey has fartballs
Michael:
Joey: I do not have fartballs! Fuck you, Michael!
When you see someone heating something in a microwave at work, home or the gas station you cup your hand around your butthole and fart. With the fart trapped in your hand you open the microwave and drop your fart. Some variations have the fartballer screaming FARTBALL at the fartballed. Others live with the quiet satisfaction that only an anonymous fartball can provide.