In ecology, the term pariah dog may refer to a dog with a pariah lifestyle: a free-ranging dog that occupies the pariah niche, which is the ecological niche based on waste from human settlements. Ecologists also have spoken of pariah birds and pariah cats. When used in this way, the term would describe a very large percentage of dogs worldwide, especially in developing countries and large parts of Eastern Europe and the Balkans.
Among dog experts, the term refers to a specific, ancient, and numerous landrace of dog native to south Asia, including Indian Pariah Dog, which has evolved features specialized to the pariah niche. When used in this way, the term applies to such dogs regardless of the lifestyle of any individual.
At other times, dog experts use the term pariah dog for ancient or primitive dog, regardless of lineage or lifestyle.
In addition, the term is used for any dog which exhibits the long-term pariah morph (LTPM), the set of characteristics typical of the Indian Pariah dog, regardless of lifestyle or ancestry.