To spontaneously shit and cum at the same time whether it be in the bed with your mate, or sitting on the seat of a toilet. Regardless your going to need some toilet paper.
“Hey man have you seengreg?”
“Yeah, he’s busy shuuming in the restroom right now”
Often used when regarding something similar to that of ‘stupid’ .However it can be used in many different circumstances and is highly based on the context it’s used in