1 definition by KinkyCactus

The rim of your anus typically with a circumference 2πr, r being the radius of the ass pussy. This has an exponential growth whether you are excreting waste, or receiving sweet love which is proportionate to each persons bum cheek volume.
Jonathan dropped the soap and felt the exponential growth of his bum lips
by KinkyCactus April 22, 2016
Get the bum lips mug.