Termed coined by french sociologist Michel Maffesoli. Its first widespread use came from his book, "Le Temps des Tribus" (1988). In it's original meaning, "urban tribes" were young city people that gathered in relatively small, fluid groups. These groups shared common interests that were, in general, different from the interests of mainstream culture.
Goths, Skinheads and Metalheads are Urban Tribes.
term coined by Ethan Watters to describe a group of individuals, usually young professionals living in large cities, that form communities to provide the emotional support of an extended family.
"Since graduating from college and moving to Chicago I haven't seen my folks, but I still celebreate holidays with my urban tribe."