An individual who for no legitimate reason thinks they're the shit because they dress, in some way, "alternativly" or have embraced some facet of alternative culture. Think high schoolers who are a walking add for Hot Topic and pretend they can skateboard. Generally irritating and dress "oddly" to gain attention of some sort.
I have nothing against indie people, goths, or even preps really, it's those kids who can't think for themselves and just follow along as alternakids that bother me.
That girl trys to talk with all the guys because she thinks she's different from everyone when really she is just an alternakid name dropping bands like My Chemical Romance!