When two lesbians have sex. Nothing goes in or out, just a lot of bumping of things.
Paula and this slut went to play bumper cars...and I watched them play all night...
(verb) bump•er car
When an enormously fat person tries to get around you in a crowded place, usually resulting in you being knocked back a few feet away by their huge love handles.
Karen: Joanie, did you see what just happened?
Joanie: Did some cuntbandit
steal your drink again?
Karen: No! Some stupid fatass just bumpercarred me right into the garbage can.
Joanie: Did you spill your drink?
Joanie: Oh, thank god.
reverse motorboating; When a woman comes up behind someone and shakes her breasts against the back of that person's head... unexpected and possibly unwelcomed.
S: "I just saw something an now it's burned into my retina's"
E: "What is it?"
S: "That girl in the green shirt just went up to that girl who's sitting down and greeted her using the bumpercar technique."