when a girls hymen is torn and starts bleeding either a little bit or a lot (depends on the girl). It is normally torn by a guys penis up the girls vagina or his fingers up it. The cherry can also pop when a girl is fingering herself, putting a tampon in, or maybe even riding a bike.

when you're hungover as shit after a spending a night drunk as a skunk

It applies to everyone except you. You virgin.
It means that oneself has lost their virginity.
A sentence you can't say: I lost my virginity!