When a motorcycle shakes its head. The front forks going from lock to lock.

A rapid side-to-side oscillation of the front wheel of a motorcycle, where the handlebars literally 'slap' the gas tank due to insufficient road grip on the front tyre.

When the fuel in a vehicle hits the inside of the tank hard enough to shake it, nearly always cause by making sudden, unplanned turns. Tank slapping is a symptom of bad driving.

Many cars use special baffles to help reduce this.

Can also include the rider's legs on a motorcycle.

The pillion passenger on a motorcycle.

see 'Tank Slapping'. The art of anal sex with a man in a doggy style.