The Old English Bulldog is an extinct breed of dog. “BULL-DOG (Canis Molossus), s. A dog of particular form, remarkable for his courage.The bull-dog is low in stature, deep-chested, and strongly made about the shoulders and thighs, the muscles of both of which are extremely developed. His head is broad, his nose short, and the under jaw projects beyond the upper, which gives him a fierce and disagreeable aspect. He is the most ferocious and unrelenting of the canine tribe, and may be considered courageous beyond every other creature in the world, for he will attack any animal, whatever be his magnitude. 1 Physical characteristics.