n. 1. The back part (usually of a vehicle) The rear end of our car was smashed when we stopped suddenly and the car behind us hit us. Often used like an adjective, with a hyphen. A head-on crash is more likely to kill the passengers than a rear-end crash.
Antonym: HEAD-ON. 2. Rump; backside. Bobby's mother was so annoyed with his teasing that she swatted his rear end.