Like many things, intent is a consideration. Hipsterism involves co-opting aspects of a culture that is not your own in a way that is amusing (to yourself and your friends while annoying others). The amusement comes from distorting the original meaning and use of the artifact or practice.
As an example, the hats. Hats cover your head for warmth and protection. The kind of hats that men wore 30 years ago for those reasons are now worn because they are from another time (which = culture in a certain sense). They also wear stocking hats, not because they are all cold, but because it is amusing to wear a stocking hat in the middle of summer.
They refer to all of this as being "ironic," which is just one more thing that they have co-opted and redefined its use and practice.
(Bottom line: if you're a slob, but you're doing it because you think it's amusing/annoying, then you're a hipster. If you're doing it because you really don't care, then you're just a slob, and that's nothing to brag about, so don't. And finally, if you are doing it because you really don't care, but you are aware that you "really don't care," then you probably really do care, which makes you a poser, which is worse than straight hipster. And you should stop doing that as well. The best option is to simply embrace what you are.)