Erupting gas exiting the anus violently. It can scratch the anus upon its departure if you decide to trust it.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.

Series of rapid farts within a short amount of time, thus fore releasing a violent butt scratch. The sound affect is that of a chainsaw, and if hard enough can feel as if a chainsaw is on ur butthole.