outgroup

1. (sociology) The group of people who do not belong to one's own social group.Examples: "This dissertation promises to correct for this theoretical deficit by formulating, elaborating, and ultimately testing a group-based moral emotions account in which white Americans’ moral appraisals of and attitudes towards racial/ethnic outgroups are considerably influenced by those of and towards fellow whites. […] On the basis of the insights from intergroup emotions theory, Chapter 3 derives and presents a series of preliminary hypotheses that are designed to test the relative importance of white shame and guilt for white Americans’ support for equity-oriented pro-black policies (e.g. affirmative action, financial reparations) and expressions of outgroup favoritism."

2. (systematics) In cladistics, all the taxa included in a study that do not belong to the ingroup that is of immediate interest.Examples: "A cladistic analysis of 45 ingroup and two outgroup taxa was performed on the basis of 134 characters."; "To study the genetic relationships among diphyllobothroid tapeworms, other members of the Diphyllobothriidae are considered, with T. solium as the outgroup."