Ah, hipsters. Where do I begin....
For a single sentence, how about: A poor collection of healthy, but lost souls with many (but mediocre) talents that seldom feature any widely practical purpose.
I seem to have more exposure to them than most people as today. For starters, they've been invading parts of my nearest metro area (Pittsburgh, PA). They particularly look for run-down areas, just above the stage where violence is overly prevalent and the where buildings are one step above condemned. Then, miraculously magical works of art and urban revitalization appear, as if sent down from the heavens above. On second thought, NOT. If they put half the energy they put into that stuff - into everyday issues facing the average American citizen - THAT would be a miracle.
On a more granular level, my personal definition of a hipster (by statistics only; individual cases may vary): Raised in suburban environments under a wide range of sheltered life circumstances, with extraordinarily and unrealistically high spirits and self esteem. And the greatest part, age 18 hits, where they decide to embark on the fabulous journey halfway across the country to some god-forsaken city (usually for university), where they move into little sheltered urban hipster communities to circlejerk each other's egos with fashion, art, science, games, and public works, supplemented by the world's finest collections of food and drink, to the tune of off-beat (yet oddly but wholly pussyfoot) styles of music.
Am I finished? Yeah, I guess. BTW this is meant to be anecdotal (everyone needs a good roast once in a while!)..