When a man abruptly and unexpectedly ejaculates in to the girl's(or man's) mouth that is sucking his penis. The recipient of this ejaculate is startled by this sudden change of events and spits the semen back up onto the man's happy trail and/or belly button.
Man is getting head and busts into girls mouth. The girl is dumfounded and spits the cum into the guys belly-button. This is an electrifying surprise for both parties and turns each other on for more intense intercourse.