Old English sheepdog

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A dog of a large sturdy breed developed in England for herding sheep, having a short or docked tail and a shaggy bluish-gray and white coat with hair typically hanging over the eyes.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun large sheepdog with a profuse shaggy bluish-grey-and-white coat and short tail; believed to trace back to the Roman occupation of Britain