The act of pressing your buttcheeks against a pane of glass and farting. This can be done while your pants are still on, but the act is best visualized without pants -- and from the other side of the glass, for optimal viewing. For an even better visual, you may perform this act while suffering from diarrhea, but be careful to avoid the inevitable splash and collateral coverage.
You know the German Squeegee Bob butt-pressed on the bank's front window? He must have had the Hershey Squirts something fierce because they still haven't been able to clean it off. Seriously, it looks like someone shot a turd at the window at Mach 3!