any of a breed of stocky, muscular, medium-sized dog, originally bred in England as a drover's dog, with a profuse, shaggy coat, usually gray or bluish gray, and a docked tail or no tail
See Old English sheepdog in American Heritage Dictionary 4
noun
Any of an English breed of sturdy dog having a docked tail and a thick, shaggy, bluish-gray and white coat with fur that hangs over the eyes.