noun. 1. essentially, any group that one isn't a member of or with which one doesn't identify, but especially a group which is considered to be different from, and insufficient to, one's own group. 2. a particular rival group which in-group members criticize, derogate, and at times, express violence against. Commonly referred to as they- group.
OUTGROUP: "The out-group seemed rather unaccepting of the young girl and her brother."