Not to be confused with the other (incorrect) definition of alternateen (which actually is an umbrella of Punk, Poserpunk, Emo, Scene, Goth, Hardcore, Grindcore, and Death Metal, all in one tight little generalization), Alternateens are the undereducated Hipsters. They look relatively indie, but stay within earth tones, have close to hippie-esque hair, and tend to say they listen to "Alternative Music" not knowing the specifics of the genre. Alternative encompasses all subgenres of rock (see whats above, give or take some). Alternateens are mostly found in small towns and are teenagers that try too hard with knowing so little about culture.
We were walking down the street in that tiny port town when we passed a teen center surrounded by Alternateens, who gave us the nastiest look.
A teenager who, in an attempt to break societal norms and quotas, dresses, acts, and listens to the same "alternative" music as the majority of other disgruntled teenagers. Piercings, unnaturally colored hair, band t-shirts and a general air of angst and contempt are usually required.
I just saw a gaggle of alternateens at the mall fondling a cardboard cutout of Limp Bizkit.