The ornamental design for a headlight for a motorvehicle, as shown and described.
FIG. 1 is a perspective view of a headlight for a motor vehicle;
FIG. 2 is an elevation view thereof from the left side;
FIG. 3 is a front elevation view thereof;
FIG. 4 is an elevation view thereof from the right side;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken line showing of the headlight for a motor vehicle is for the purpose of illustrating portions of the headlight for a motor vehicle and forms no part of the claimed design.