Back"board` (&?;), n. [2d back, n. +
1. A board which supports the back when one is
specifically, the board athwart the after part of a boat.
2. A board serving as the back part of anything, as
of a wagon.
3. A thin stuff used for the backs of framed
pictures, mirrors, etc.
4. A board attached to the rim of a water wheel to
prevent the water from running off the floats or paddles into the interior
of the wheel. W. Nicholson.
5. A board worn across the back to give erectness
to the figure. Thackeray.