tank-slapper

Noun

tank slapper (plural tank slappers)

1. A phenomenon resulting from inadequate dampening of the steering of a motorcycle at high speed. This results in the violent oscillation of the handlebars from left to right, so that they make contact with the gas tank, which is situated on the chassis between them.
2. A phenomenon that occurs when a vehicle loses and regains traction at the rear of the car, whilst the front retains traction.