From The Collaborative International Dictionary of English v.0.48:
Bumper \Bum"per\, n. [A corruption of bumbard, bombard, a large
drinking vessel.]
1. A cup or glass filled to the brim, or till the liquor runs
over, particularly in drinking a health or toast.
[1913 Webster]
He frothed his bumpers to the brim. --Tennyson.
[1913 Webster]
2. A covered house at a theater, etc., in honor of some
favorite performer. [Cant]
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48:
Bumper \Bump"er\, n.
1. That which bumps or causes a bump.
[1913 Webster]
2. Anything which resists or deadens a bump or shock, such as
a metal or rubber rim extending from an object; a buffer.
[1913 Webster]
3. Specifically: (Motor vehicles) A protective guard device,
usually of metal or rubber, attached horizontally to the
front or rear of the frame of a vehicle, designed to
resist or deaden a bump or shock, and to prevent damage to
the main frame of the vehicle in low-velocity collisions.
[PJC]