The ornamental design for a pillow, as shown and described.
FIG. 1 is a top, right-side perspective view of a pillow, according to one embodiment of the present invention;
FIG. 2 is a front plan view of the pillow of FIG. 1;
FIG. 3 is a back plan view of the pillow of FIG. 1;
FIG. 4 is a right plan view of the pillow of FIG. 1;
FIG. 5 is a left plan view of the pillow of FIG. 1;
FIG. 6 is a top plan view of the pillow of FIG. 1; and,
FIG. 7 is a bottom plan view of the pillow of FIG. 1.
The broken lines shown in the drawings are shown for illustrative purposes only and form no part of the claimed design. In addition, the surface shading, if any, illustrated in the drawings is provided merely to highlight the contour of the design; it is not intended to be illustrative of texture or gloss.