backboard

backboard is a   Noun

Definition:

[1] A board which supports the back wen one is sitting;

[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 paddies into the interior of the wheel. W. Nicholson.

[5] A board worn across the back to give erectness to the figure. Thackeray.

Synonyms: