A slug is a term used for a bulky solid ballistic projectile. It is "solid" in the sense of being composed of one piece; the shape can vary widely, including partially hollowed shapes. The term is occasionally applied to bullets, but is most commonly applied to one-piece shotgun slugs, to differentiate them from shotshells containing numerous shots. Slugs are commonly fired from choked smoothbore barrels, but some specially-designed slug barrels have riflings that can impart gyroscopic spin required for in-flight stability.