The shimmy is one of the signature moves of belly dance. It is where you shake a certain part of the body very quickly. A shimmy is usually isolated to a specific part of the body such as the hips or chest. Shimmies can be performed by going up and down or front to back. According to Wikipedia, a shimmy can be either rhythmic or arrhythmic.
Below is an example of an up-down shimmy of the hips. The model uses small dancer steps to show you what a shimmy looks like from all angles. Basically, she simply shook her hips up and down really fast, more or less to the beat of the music and while she shook her hips she turned in place.Performed by Tiffany Hijak