Brain herpes is something unpleasant that you haven't thought of in a while that pops into your head every once in a while. You can't unsee it, unhear it, etc. Once you contract a brain herpes, it is with you for life.
Examples of brain herpes include: goatse, that fucking Barbie Girl song, the image of when you walked in on your parents mid-coitus, etc.
by Pho King Guy June 2, 2010
When a moron says something so stupid you fear you might have become slightly stupider just for having heard it
James H. asked me what the difference between marshmallows and mushrooms was and now I need to get tested for brain herpes
by Betty Thorny November 4, 2010