A combination of falling and bouncing; A founce is when a guy and a girl are hooking up. They are passed third and heading for home. Suddenly, they are getting so frisky that the girl falls off the bed. She is so embarrassed that she grabs her clothes and bounces.
Justin was stoked, he was about to seal the deal and out of nowhere, Jen founced and left Justin to sulk in his bed wearing only boxers.