Concave
CONCAVE, adjective [Latin Hollow. See Cave.]
1. Hollow, and arched or rounded, as the inner surface of a spherical body; opposed to convex; as a concave glass.
2. Hollow, in a general sense; as the concave shores of the Tiber.
3. In botany, a concave leaf is one whose edge stands above the disk.
CONCAVE, noun A hollow; an arch, or vault; as the ethereal concave
CONCAVE, verb transitive To make hollow.