toy dog, classification used by breeders and kennel clubs to designate very small breeds of dogs kept as pets. Some are selectively bred diminutive forms of larger breeds and others are naturally small. The following breeds are designated as toy dogs by the American Kennel Club: affenpinscher, Brussels griffon, Chihuahua, English toy spaniel, Italian greyhound, Japanese spaniel, Maltese, miniature pinscher, papillon, Pekingese, Pomeranian, pug, Shih Tzu, silky terrier, toy poodle, toy Manchester terrier, and Yorkshire terrier. See dog.