circumcision /-sizh″ən/ [L, circum, around, cadere, to cut] , a surgical procedure in which the prepuce of the penis is excised. Circumcision is widely performed on newborn boys. The operation is performed on newborns with penile block anesthesia, using one of several kinds of clamp. It is sometimes performed on adult males in the treatment of phimosis and balanitis. Ritual circumcision is required by the religions of approximately one sixth of the world’s population.