granfalloon
A group of two or more people who imagine or are manipulated to believe they share a connection based on some circumstance of little or no real significance.
Gamers are nothing but members of an enormous granfalloon. The word [gamers] totally fails to accurately describe anything about a person when it comes to capturing their interests in interactive entertainment, and yet many gaming enthusiasts cling to the term and make it a facet of their identity.
Where it comes from
Coined by American writer Kurt Vonnegut in 1963, in the novel Cat's Cradle, in which Vonnegut described the term as referencing a false karass, or "a proud and meaningless association of human beings"; later adopted by market researchers and social scientists.
Adapted from the Wiktionary entry granfalloon (CC BY-SA 4.0).