In a cladistic analysis, any taxon used to help resolve the polarity of characters, and which is hypothesized to be less closely related to each of the taxa under consideration than any are to each other.

A group to which a person does not belong and toward which the person may feel a sense of competitiveness or hostility.

A taxon that separated from another taxon, whose lineage is to be inferred, before the latter underwent evolutionary radiation.

A social group with which one does not identify or to which one does not belong.