The raw tender period that your anus goes through after you have a violent bowel movement, resulting in tenderness of the anus where you cannot sit down for a few minutes following. You must stand still and wait for the feeling to go away.
"Guys, I can't sit down yet, I have Supplebutt"
"I will have a seat once my Supplebutt goes away"
"Oh man, I've got serious Supplebutt, give me a few minutes to recover before we go anywhere"