The act of masterbation while watching a reflection of yourself preform the act. Most commonly this is purpotrated in a hotel room in front of a mirror.
*door opens*
Connor: So Craig what are you doing in...OH MY GOD! WHAT THE HELL?
Craig: I was, eh, um, er...
Connor: YOU WERE WANKING OFF TO YOUR OWN REFLECTION!
Craig: I was just...er...
Connor: That was a Valkenburg Mirror you sick...I MEAN FOR FUCKS SAKE WHAT YOU WERE THINKING?!
Craig: Um...
Connor: So Craig what are you doing in...OH MY GOD! WHAT THE HELL?
Craig: I was, eh, um, er...
Connor: YOU WERE WANKING OFF TO YOUR OWN REFLECTION!
Craig: I was just...er...
Connor: That was a Valkenburg Mirror you sick...I MEAN FOR FUCKS SAKE WHAT YOU WERE THINKING?!
Craig: Um...
by Mark Murray - WOW Champion November 8, 2008