The ornamental design for a lawnmowerblade, as shown and described.
FIG. 1 is a perspective view of a lawnmower blade, showing our new design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a front side elevation view thereof;
FIG. 5 is a rear side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown in the drawings represent unclaimed environment only and form no part of the claimed design. The surfaces are lightly lined for contour only. No claim is made to surface texture of the particular design.