bumper Definition

(Brit)
1. A bar on the front or back of a motor vehicle which lessens the shock or damage if it hits anything.
2. A pad fitted around the inside of a cot to prevent a baby from bumping itself against the bars.
(US)
3. A railway buffer.
4. Something or someone that bumps, eg in cricket a delivery that bumps.
5. An exceptionally good or large example or measure.

1. Exceptionally good or large.

Example: a bumper edition

Said of traffic: in or consisting of solid queues, one car behind the other.