Flava Flav's Public Enemy catchphrase. It usually starts the shit, with Termanator X and Chuck D bringing it afterwards. However, anyone can say it, as long as you mean it. It is one of the most positive things you can say. It's the best.
Chuck D- Somebody in the house say yeah. If you really like to rock the funky beats, somebody in the house say HELL YEAH.
Flava Flav- YEEEEEEEEEEEEEEEEAH BOYYYYYYYY
Friend- You want to go get some tacos and tequila?
You- YEAH BOY