Concave

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.

1. A hollow; an arched vault; a cavity; a recess.
2. (Mech.) A curved sheath or breasting for a revolving cylinder or roll.

1. To make hollow or concave.