The ornamental design for a pillow, as shown and described.
FIG. 1 is a left side perspective view of a pillow showing my new design, the right side view being a mirror image thereof;
FIG. 2 is a front perspective view of the pillow of FIG. 1;
FIG. 3 is a left side perspective view of the pillow of FIG. 1;
FIG. 4 is a bottom perspective view of the pillow of FIG. 1;
FIG. 5 is a top, rear, left side perspective view of the pillow of FIG. 1 with a rear seam partially open revealing hook and loop fastener strips and semi-cylindrical cushions;
FIG. 6 is a bottom, front perspective view of the pillow of FIG. 1 in an alternate position of use with the rear seam fully open and the semi-circular cushion members separated; and,
FIG. 7 is a bottom, left perspective view of the pillow of FIG. 1 showing it in use with a seat belt received between the semi-cylindrical cushions.
All broken lines in all figures are included for the purpose of illustrating environment and unclaimed features of the design and form not part of the claimed design.