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.-hollow; void of contents.-a hollow; an arched vault; a cavity; a recess.-a curved sheath or breasting for a revolving cylinder or roll.-to make hollow or concave.