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.

When you eat dirt for the first time and leave your family to build a shack in the woods

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.