Verb. To culminate sexual intercourse by a male by ejaculationinternally in the receiving partner's mouth, then slapping the receiving partner's face before the penis becomes flaccid.
"Why are Cindy's cheeks all red?"
"Her b.f. likes to 'pop 'n flop'."
"Why are her cheeks still red?"
"He just popped in to pop 'n flop her 5 minutes ago!"