Rock Boss
The Rock Boss is used to describe the biggest and toughest prisoner on the yard. In order to become the Rock Boss, a challenger must face the current Rock Boss in mortal combat. If the challenger defeats the Rock Boss, he then becomes the new Rock Boss.
"If you don't toss the Rock Boss's salad, he's gonna beat and torture you."
"That guy's the Rock Boss. The guard's don't even mess with him."
"That guy's the Rock Boss. The guard's don't even mess with him."