Also found in: Thesaurus, Idioms.
1. Traveling close together with bumpers almost touching: The cars were bumper-to-bumper in the tunnel.
2. Moving slowly or stalled as a result of tight spacing between vehicles: bumper-to-bumper traffic.
(of traffic) forming long, slow-moving queues
marked by a long line of cars moving slowly or with many stops and starts, one behind the other: bumper-to-bumper traffic.