When a female with an incredibly big butt chin, puts a penis in the crack with a little lubericant (usally spit, baby oil, or non-scented lotion) an does and up an downward motions thus making the penis ejaculate all over the females face.
Trey: Hey did you hear?
Alex: Hear what bro?
Trey: Ashlyn gave Luke a chinjob, and he had to be rushed to the ER.
Alex: Oh. Wow what thats awful, but those are very dangerous.