When the top of the head, or dome, is blown off by either 1) a bowl of good marijuana, or 2) a high caliber rifle round.
"The Marine Recon sniper smoked a bowl of marijuana and popped his top, and then aimed down the scope of his rifle and at a haji a mile away and... POP TOP!"
by domepoppa January 23, 2010
The hymen of a virgin female human.
"She's so fresh, I bet she still has a pop-top."
by dustinzmann April 29, 2010