rear end

[rear end] {n.} 1. The back part (usually of a vehicle)

The rearend of our car was smashed when we stopped suddenly and the car behindus hit us.

- Often used like an adjective, with a hyphen.

Ahead-on crash is more likely to kill the passengers than a rear-endcrash.

Contrast: HEAD-ON. 2. Rump; backside.

Bobby's mother was soannoyed with his teasing that she swatted his rear end.