Concave

Part of speech: noun (n.)

1. A hollow; an arched vault; a cavity; a recess. Up to the fiery concave towering hight. Milton.

2. A curved sheath or breasting for a revolving cylinder or roll.

Part of speech: verb (v.)

To make hollow or concave.

Part of speech: adjective (a.)

1. Hollow and curved or rounded; vaulted; -- said of the interior of a curved surface or line, as of the curve of the of the inner surface of an eggshell, in opposition to convex; as, a concave mirror; the concave arch of the sky.

2. Hollow; void of contents. [R.] As concave . . . as a worm-eaten nut. Shak.