The ornamental design for a toothbrush, as shown and described.
FIG. 1 is a front view of the toothbrush of the present invention;
FIG. 2 is a back view thereof;
FIG. 3 is a plane view thereof;
FIG. 4 is an enlarged left side view thereof;
FIG. 5 is an enlarged right side view thereof;
FIG. 6 is an enlarged cross-sectional view thereof along lines 6—6 shown in FIG. 1;
FIG. 7 is an enlarged cross-sectional view thereof along lines 7—7 shown in FIG. 1;
FIG. 8 is an enlarged cross-sectional view thereof along lines 8—8 shown in FIG. 1; and,
FIG. 9 is a perspective view thereof.
The broken line showing of a bristled head is included for the purpose of illustrating a portion of the article that forms no part of the claimed design.