Top Definition
The scientific explanation for the rattling of house windows when a car with a system passes down the street. Can also happen from inside windows to outside of the car. Also, when someone has nerve to put a system on a piece of shit car, the banging sounds can create racket along with loose parts on the car.
I was watching tv in my friend's livingroom and suddenly the windows began to vibrate and I heard very loud bass. I said, "Charlene, what the hell is that noise?!" and she goes, "Don't worry sara, it's just bumptivity. It's normal in the ghetto." Boy was I relieved.
by lv2ja2003 January 23, 2008

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