Băck'bōard, n.

noun

n. [back and board.]

A board placed across the after part of a boat for the passengers to lean against.
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. Nicholson.
A board worn on the back to give erectness to the figure. Thackeray.
A part of a lathe.