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.
"I used to hate my boss. Then I started fartballing his afternoon coffee and I feel better."