The ornamental design for a hairdryer, as shown, and described.
FIG. 1 is a perspective view of the hair dryer;
FIG. 2 is a side view of the hair dryer;
FIG. 3 is a front view of the hair dryer;
FIG. 4 is a rear view of the hair dryer;
FIG. 5 is a top view of the hair dryer;
FIG. 6 is a bottom view of the hair dryer;
FIG. 7 is a perspective view of the hair dryer with the exterior housing of the barrel portion in a ninety-degree rotated position;
FIG. 8 is a side view of the hair dryer;
FIG. 9 is a front view of the hair dryer;
FIG. 10 is a rear view of the hair dryer;
FIG. 11 is a top view of the hair dryer; and,
FIG. 12 is a bottom view of the hair dryer.
The dashed broken lines depict environment and form no part of the claimed design. The use of dot-dot-dash broken lines defines the bounds of the claimed design and form no part thereof.