Analagous to the f stops on a camera,this refers to aperture settings built in to the anus.These f stops vary with the load. An f-1 would be used to pass a tapeworm while an f-11 would be needed for a loggerhead turd. Butthole f stops can get out of sync with excessive anal sex which can and often does result in turd whittling.(passing a turd through too small of orifice)
by wolfbait51 June 7, 2011