The act of moving your ass up and down rapidly like you are having a seizure.
1) Dad why is that retarded giraffe with its tongue hanging out rubbing its ass on Robin Thicke? Actually son that is Miley Cyrus, it is called twerking and it is pretty much the type of thing that has been celebrities do for attention.
2) Quick someone call 911, that girl over there is having a seizure, her ass is moving out of control. Everyone stay calm, that is just what we call twerking. It's what girls who are desperate for attention do.