Pigskins, also referred to as footballs, can have several synonyms. One common synonym is the phrase "the rock," which is a nod to the hardness and density of the football. Other synonyms include "the pill," "the pig," and "the bladder." All of these descriptors are traditionally used by football players and enthusiasts to describe the ball used in the game. In addition to the traditional leather material of footballs, some modern versions of the ball are made from synthetic materials or a combination of leather and synthetic materials. Despite the variations in materials, the term "pigskin" has remained a popular term used to describe the football.