Con″cave (kŏṉ‐kā‐v″ or kŏn″–; 277), a. [L. concavus; con- + cavus hollow: cf. F. concave. See Cave a hollow.] 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.
As concave... as a worm-eaten nut.
Shak.