Definition: A board which supports the back wen one is sitting;
Definition: A board serving as the back part of anything, as of a
wagon.
Definition: A thin stuff used for the backs of framed pictures,
mirrors, etc.
Definition: A board attached to the rim of a water wheel to prevent
the water from running off the floats or paddies into the interior of
the wheel.
Definition: A board worn across the back to give erectness to the
figure.