When a male is laying down on his back, and blows a load on his belly button. Girl dips her nipples in his belly buttonand then puts them in his mouth.
When someone is dating someone that is either too ugly, old, young, or just plain wrong for them. It can also be used when you're dating someone in a much lower socio-economic class or someone of a different race or level of intelligence.
Fred: Dude, so who're you into these days?
Tim: This freshman in high school. She's really cute.
Fred: Gross... you're a sophomore in college. Way to start dippin' in the fondue.