pop (one's/someone's) cherry
1. vulgar slang (of someone else) To have sexual intercourse with a virgin, especially a female. Before you go popping a girl's cherry, you had better make damn sure that you and she are both totally ready to sleep with each other.
2. vulgar slang (of oneself) To have sexual intercourse for the first time. There is nothing wrong with waiting until you're absolutely ready before you pop your cherry. Too many people try to pressure you into it from too young an age.
3. vulgar slang (of oneself) To do something for the first time, especially that which is particularly daunting, difficult, dangerous, or illegal. Somebody pass Marcus the joint, he still needs to pop his cherry tonight! For her birthday, I bought my friend Samantha a voucher so she could pop her cherry sky diving.