The ornamental design for a pillow, as shown and described.
FIG. 1 is a front perspective view of a pillow, in accordance with an embodiment of the present disclosure;
FIG. 2 is a left side view of the pillow of FIG. 1;
FIG. 3 is a right side view of the pillow of FIG. 1;
FIG. 4 is a front view of the pillow of FIG. 1;
FIG. 5 is a rear view of the pillow of FIG. 1;
FIG. 6 is a top view of the pillow of FIG. 1;
FIG. 7 is a bottom view of the pillow of FIG. 1;
FIG. 8 is a left perspective view of the pillow of FIG. 1 with its two covers partially broken away to show respective two separable foam pads beneath the covers; and,
FIG. 9 is a left exploded perspective view of the pillow of FIG. 1 with its two pillow sub-units detached from each other along a zipper.
The jagged broken lines are depicted in FIG. 8 to represent a partial view of covers of the claimed design in order to reveal obscured portions of the claimed design.