Concave

(82), a. [Fr. concave, Lat. concavus, from con and cavus, hollow. See CAVE.] Hollow and curved or rounded; — said of the interior of an arched surface, or of a curved line, in opposition to convex; as, a concave mirror.

n. [Lat. concavum.] A hollow; an arched vault. “Up to the fiery concave towering high.” Milton.

[imp. & p. p. CONCAVED; p. pr. & vb. n. CONCAVING.] To make hollow. Seward.