can you really define an ever changing entity
probably not, but you can have a definition attempt be farther from reality than others.
this is probably the closest anyone in this thread has come to defining "hipster."
don't want to be whimsical or some crap like that, but hipsters have existed for most of the 20th century, and were probably born alongside "pop" or "popular culture." it seems that each generation of hipsters is defined by the popular culture they are subversive to in that they reject the present idea of pop and those exploits the fans of pop partake in in favor of a culture they deem more artistic, intelligent, authentic, stylistic, blah blah blah... As a result of their refusal to completely conform with a generally large mass of the population and their particular taste they are identified through blanket terms.
a pretty recent change in popular cultures paradigm shift is immediately apparent in Seinfeld. "Hipster doofus" is a term pretty familiar to all of us who are fans of the show, and presents a portrait of a much different character or stereotype than the ever morphing present day "hipster."

hipster doofus
vs.

vs.

vs.

as for the "non-athletic" comment, i know plenty of people, myself included, who have been called hipsters that are above-average athletes. so don't think that really explains the whole picture.