Snowboard or Splitboard

FIG. 1 is a top perspective view of an ornamental design for a snowboard or splitboard; FIG. 2 is a top plan view thereof; FIG. 3 is a first side view thereof, the opposite, second side view being a mirror image of the first side view; FIG. 4 is a rear view thereof; FIG. 5 is an enlarged view of the encircled area 5 in FIG. 1 ; and, FIG. 6 is an enlarged view of the encircled area 6 in FIG. 4 . The bottom surface of the snowboard or splitboard, not shown, forms no part of the claimed design. The broken lines are for purposes of illustrating environmental structure and form no part of the claimed design.