There is a profusion of words and phrases used for dogs that are not purebred . The words cur, tyke, and mongrel are generally viewed as derogatory in America, whereas in the United Kingdom mongrel is the unique technical word for a mixed-breed dog, so is not a term of disparagement. Many American owners prefer mixed-breed. Mutt is also used (in the U.S.A and Canada), sometimes in an affectionate manner. In Hawaii, mixed breed dogs are referred to as poi dog, and in the Bahamas, they call them Pot Cakes(referring to the table-leftovers they are fed). Some American registries and dog clubs that accept mixed-breed dogs use the breed name All American, referring to the United States' reputation as a melting pot of different nationalities. In South Africa, the tongue-in cheek expression pavement special is sometimes used as a description for a mixed-breed dog. Random-bred dog, mutt, and mongrel are often used for dogs who result from breeding without the supervision or planning of humans, especially after several generations, whereas mixed breed and crossbreed often imply mixes of known breeds, sometimes deliberately mated.In Brazil and the Dominican Republic, the name for mixed-breed dogs is vira-lata (vira: to turn, to bring down; lata: tin can, trash can) because there are dogs without owners that feed on urban garbage on the streets, and often knock over trash cans to reach the food. Therefore, by having stray dogs it seems to increase the amount of "mixed-breed" dogs.Slang terms are also common. Heinz 57 is often used for dogs of uncertain ancestry, in a playful reference to the "57 Varieties"slogan of the H. J. Heinz Company. In some countries, bitsa (or bitzer) is common, meaning "bits o' this, bits o' that". A fice orfeist is a small mixed-breed dog.To complicate matters, many owners of crossbred dogs identify them—often facetiously—by an invented breed name constructed from parts of their parents' breed names. For example, a cross between a Pekingese and a Poodle is called aPeekapoo, possibly a play on peek-a-boo, along with the Goldendoodle, a cross between a poodle and a golden retriever. As another example, one of the UK's Queen Elizabeth's famous Corgis mated with her sister's Dachshund, and the resulting offspring are referred to as Dorgis.
I got this information from:http://en.wikipedia.org/wiki/Mixed-breed_dog