1. Originally meant to refer to the type of pop-folk music one might hear from artists and bands that would play at Lilith Fair
, i.e. mostly acoustic music with supposedly deep meanings. So named because fans of this style of music were known to be passionate about wearing Birkenstock shoes in the late 90's when Birkenrock was the genre du jour.
2. Now, the word is expanded to also include slightly more testosterone-laden acts (but only slightly). In addition to the Lilith acts, acoustic male acts that a little bit too positive to be emo
Angela owns every Indigo Girls bootleg ever made. She's really into that Birkenrock.