Mongrelism
A mongrel, mutt, or mixed-breed dog is a dog that belongs to no single organizationally recognized breed and is not the result of selective breeding.
Read more about Mongrelism: Mixed-breed Vs. Crossbreed, Mongrels Vs. Mixed Breeds, Regional and Slang Terms, Appearance, Determining Ancestry, Health, Types of Mongrels, Mixed-breeds in Dog Sports, Advantages and Drawbacks