The act of spreading the partner's butt cheeks apart and proceeding to slap the anal hole sternly and repeatedly until it puckers like an indecisive budding flower. At this point you gently place your nuts onto the anal hole and have the partner flex as hard as he/she can. Thus the entire scrotum is enveloped from sight. Once this is achieved, you pull away as fast as you can resulting in a mutual feeling of slight discomfort and discovery.
"Man, I am realy sore from all those purple wonderfuls!"