Generally adolescents aged 15-20 who are involved in the "scenes" surrounding emo and indie (occasionaly other types of music as well, including punk with it's mohawked fashion punks) for whom the scene is more important than the music itself. They place greater importance upon the style of dress, knowledge of "cool" bands and being a part of the scene than the music that is the centre of the scene. They are the death of many scenes and are to be shunned.
He's such a scenester! He spends all his cash on scarves! Damned emo kids.