any of various usually long-haired breeds of dog reared to herd and guard sheep
a type of domestic dog This article discusses the domestic dog
A dog trained to guard and herd sheep.
a dog trained to help a shepherd watch and tend sheep
A Sheep dog is a type of domestic dog whose original purpose was to herd or guard sheep. Sheepdogs are just one category of herding dogs. Many sheep dogs are now kept as domestic pets or companion dogs.