It's when two people are going at it doggie style, & the guy throws up all over the girl because he drank way too many Jäger bombs & played too much beer pong.
"The other night at Billys man, I got so chocolate wasted... I took this chick upstairs, & we were goin at it, I had her on her face. & right when she screamed my name, I puked right on the back of her head."
"Damn, you pulled a New Mexican college student."