mastiff (măsˈtĭf) [key], breed of very large, powerful working dog developed in England more than 2,000 years ago. It stands from 27 to 33 in. (68.6–83.8 cm) high at the shoulder and weighs from 165 to 185 lb (74.9–83.9 kg). Its coarse, short, close-lying coat may be silver fawn, apricot, or dark fawn brindle in color, with a black muzzle, nose, and ears and black around the eyes. The mastiff was first bred as a fighting dog and guardian. As a fighter it was cited for its physical prowess and courage by Caesar in his account of the Roman invasion of Britain in 55 B.C. Indeed, it was later imported to Rome to fight in the arena. In its native country the mastiff was a popular antagonist in bullbaiting and bearbaiting contests and in organized dogfights until these blood sports were outlawed in 1835. However, throughout the entire history of the breed in England its greatest popularity has derived from its widespread use as a guardian of home and family. This centuries-old association with man is undoubtedly responsible for the mastiff's unexcelled suitability for the role of family companion and its particular devotion to and gentleness with children. The term mastiff is also applied to a general type of giant dog whose origin has been traced to Asia and of which the modern Tibetan mastiff, infrequently seen in the United States, is representative. See dog.