When fucking a girl in the vagina, and you in one sly, dastardly, and courageous movement you remove the penis from the vagina, and instantly slip it into her asshole.
*note* unless the girl has a wide girth...this move should follow the spit prep
"so i totally burrow jumped this girl last night, she loved that shit."
When you fuck a girl from behind and spit directly into her ass, for lubrication to perform a "Burrow jump".
Guy - bend over baby
Girl - okay
*PTEW*
Girl - Did you just...spit prep me?
Guy - yes i did 3:D