Pop your blueberries
When a male loses his virginity. It is the male equivalent of "having your cherry popped." The term "blueberries" is used to refer to testicles, being "blue" from never previously having sex.
Example 1: "When are you finally going to pop your blueberries, bro?"
Example 2:
Person 1: "How old were you when you popped your blueberries?
Person 2: "I was 16."
Example 2:
Person 1: "How old were you when you popped your blueberries?
Person 2: "I was 16."