The ornamental design for a radiatorgrill for an automobile, as shown and described.
FIG. 1 is a front elevational view of a radiator grill for an automobile in accordance with my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a front-left-bottom side perspective view thereof; and,
FIG. 7 is a front-right-top side perspective view thereof.
The broken line showing of the radiator grill is for purpose of illustrating environmental structure and forms no part of the claimed design. The rear view of the radiator grill forms no part of the claimed design.