turtleback

noun

1. Anything having the shape of a turtle's back (that is, its shell).

2. (nautical) A convex deck at the bow or stern of a vessel, designed to shed seawater quickly.

3. A primitive stone celt of a form suggesting the back of a turtle.

4. A library binding of a mass market paperback with a generic hardcover.

- (The addition of quotations indicative of this usage is being sought):

5. Any plant of the genus Psathyrotes of annual and perennial forbs and low subshrubs native to dry areas of southwestern North America.