Undergarment

1. 1The ornamental design for an undergarment, as shown and described.

FIG. 1 is a perspective view of an undergarment;
FIG. 2 is a left side view of the undergarment, the right side view of the undergarment being a mirror image of FIG. 2;
FIG. 3 is a top view of the undergarment;
FIG. 4 is a front view of the undergarment;
FIG. 5 is a rear view of the undergarment; and,
FIG. 6 is a bottom view of the undergarment.