The area near your dick/VJ where your zipper bulges up usually when you sit down and makes it look like you have a HUGE erection. this is for both men and women but if your a woman and your not lady gaga nobody will think you actually have an erection so really only men have a problem with this.
man near you: "Dude, What the hell control your dick"
you: "dont worry man, its just my zipper dick"
the painful outcome while dryhumping: a bit of skin from the dick gets caught in the teeth of your zipper from the inside of the jeans.
i was going to go all the way but after i got zipper dick i was too sore to move.