The ornamental design for a rearbumper for an automobile, as shown and described.
FIG. 1 is a front elevational view of a rear bumper for an automobile showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational thereof;
FIG. 6 is a top, front and right side perspective view thereof; and,
FIG. 7 is a bottom, front and left side perspective view thereof.
The rear view of the rear bumper forms no part of the claimed design since it will not be visible once the rear bumper is mounted to an automobile. The inside surfaces of the rear bumper, visible in FIGS. 2, 3, 6, and 7, form no part of the claimed design since the inside surfaces are hidden when the rear bumper is mounted to the automobile.