, urban dictionary quote, did you end up with saggy flaps then
A Wizard's sleeve is firstly and foremost the section of a wizard's cloak that covers the shoulder down to the hand. It is normally tapererd in that when looking at it, it widens as it gets closer to the hand.
An urban or slang use of the term Wizard's Sleeve is to describe women's vaginal flaps once they are in a particularly saggy state due to being over worked in a sexual manner or after giving birth to a number of children.
"After six kids, her fanny must hang like a Wizard's sleeve"