Pit bull is a word used to describe several breeds of dog. This includes the American Pit Bull Terrier, American Staffordshire Terrier, American Bully and Staffordshire Bull Terrier, and dogs with a mix of these breeds. In some locations, the modern American Bulldog and Bull Terrier are described as a "pit bull-type dog". Pit bull can also mean dogs that were known as "bull terriers" before the development of the modern Bull Terrier in the early 20th century.