a horizontal bar fixed across the front or back of a motor vehicle to reduce damage in a collision

she started the car with a jerk and hit the bumper of the car in front

a flat race for inexperienced horses which are intended for future racing in hurdles or steeplechases

a generous glassful of an alcoholic drink, typically one drunk as a toast

exceptionally large, fine, or successful

a bumper crop

everyone in the business predicts a bumper year