what every middle schooler and high schooler does at school dances. basically that boy gets behind the girl and he puts his hands on her hips and they rock from side to side. it's supposed to mimic sex. the teachers hate it.
Bob- dude i was grinding so hard on some chick last night!
john- did you stick your boner up her butt?
bob- we did it through the whole song!
John- wow, i bet you feel guilty, after all you're only a 7th grader!