(bum′pər) noun
1. Something that either bumps or causes a bump.
2. A buffer, as on a railroad car.
3. A guard on the front or rear of an automobile to attenuate the shock of collision.

(bum′pər) noun
A cup or glass filled to the brim.
—adjective Unusually full or large: a bumper crop.
—v.t.
1. To fill to the brim.
2. To drink toasts to.
—v.i.
3. To drink from bumpers. [? Alter. of F bombarde large cup, infl. in form by BUMP]