guard dog, watchdog - a dog trained to guard property

Doberman, Doberman pinscher - medium large breed of dog of German origin with a glossy black and tan coat; used as a watchdog

miniature pinscher - small German version of a Doberman pinscher

affenpinscher, monkey dog, monkey pinscher - European breed of small dog resembling a terrier with dark wiry hair and a tufted muzzle