A penis the size of a toothpick when 100% erect, also meaning "gay" or "queer", can also mean no penis at all.
"Man! Don't whip out that Valkenburg! Its discusting!"
by Brandon V March 12, 2007
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 08, 2008