To me, a "hipster" is someone who is utterly consumed by the superficial - music, clothes, body art, etc - and judge quality mostly by the basis of exclusivity, or failing that, outright oddity. They consider obscure or strange to be the same as good, or wear and consume the deliberately tacky "ironically" - as if it's a show of sophistication. Ugly brand new vintage t-shirts referencing an obscure TV high school, and especially a sports team or marching band derived from it, knit caps for weather at least 30 degrees cooler than it well ever get locally, scarves in summer. It's a way of signaling, "I'm quirky, unique, and have eclectic tastes, just like everyone I know and want to associate with!" You can say the same about any sub-culture, except with hipsters, it really doesn't get any deeper than that. It's all about one-upping each other with obscurity or inanity done "ironically" - and naturally, they badly misuse the entire concept of irony. It's pure self-indulgence and very often, at least in the kids I see at the college, done with someone else's money.
To quote Dale Gribble: "They walk slow because there's nowhere they gotta be, man."
I think the other thing is, the only things they seem to enjoy, or get eager about, is tearing down others. Seriously, a hipster will talk about going to a party someone's throwing, and inviting them to, "ironically". I guess the thought process is that they're so cool, the party's lame, but that because they're attending a lame party disingenuously, as an inside joke, it's okay.
Fuckers.