High Quality Content by WIKIPEDIA articles! The Bull Terrier or English Bull Terrier is a breed of dog in the terrier family. They are known for their large, egg-shaped head, and small triangular eyes. The Bull Terrier is exceptionally powerful for its size, ranking 1st out of all dog breeds in pound-for-pound lean muscle tissue. There is also a miniature version of this breed and is officially known as the Miniature Bull Terrier.