Can be administered with either hand but the act of slapping someone in the back of the head. Depending on the speed of the hand it can also be called a "0-90" (meaning the hand accelerates to 90 mph before striking the back of the head). A perfectly administered "skull pop" will most of the times cause the head to jerk forward.
I was just sitting here minding my own bitnis and Medo came up from behind and skull popped me.
You better get your ass home. Dads pissed and I think he'll be dishing out skull pops like candy.