When you are going down on a chick and she is getting close to climaxing, you lift her bottom and torso area so that her head is lower than her waist (think 45 degree angle) and you dump pop rocks and cola in her chewbacca and you shake her pelvis around. It helps her reach climax faster and it's an awesome sciece project.
Man 1 "Oh man, my lady was freaking out the other night after I gave her a foaming chewbacca."
Man 2 "Foaming chewbacca? What's that?"
Man 1 "Pop Rocks and Cola, man. Pop rocks and cola."
After laying some serious pipe with Amanda, she was still horny so I foamed the milk a little bit.
During vaginal intercourse, the female produces a filmy, white lubricant. Upon completion, applying the lips, tongue, and mouth to the vagina is an act known as 'foaming the milk'.