The ornamental design for a washbasin, as shown and described.
FIG. 1 is a perspective view of a wash basin showing my new design;
FIG. 2 is another perspective view of the wash basin seen in FIG. 1;
FIG. 3 is a right side elevational view of the wash basin seen in FIG. 1, the left side elevational view being a mirror image thereof;
FIG. 4 is a front elevational view of the wash basin seen in FIG. 1;
FIG. 5 is a rear elevational view of the wash basin seen in FIG. 1;
FIG. 6 is a top plan view of the wash basin seen in FIG. 1; and,
FIG. 7 is a bottom plan view of the wash basin seen in FIG. 1.
In the drawings, the broken lines depict portions of the wash basin that form no part of the claimed design. Shade lines, having a combination of long and short lines in the drawings, show contour and not surface ornamentation.