A large, ugly pimple that develops on the ass if you haven't been washing for a while.
It doesn't hunt, but will
otherwise annoy until finally popped (usually with fire).
If you don't continue to wash, it'll come back in six weeks.
Person 1: Dude, my ass is annoying the fuck outta me.
Person 2: I think you got an MNG on
your ass. You should
pop that shit and start washing your ass, you greasy
motherfucker.