Meaning of CONCAVE in English
( a. )
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.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012