1. (n.) A board which supports the back when one is sitting;

2. (n.) A board serving as the back part of anything, as of a wagon.

3. (n.) A thin stuff used for the backs of framed pictures, mirrors, etc.

4. (n.) 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.

5. (n.) A board worn across the back to give erectness to the figure.