Definitions
1.nounA concave surface or curve.
2.nounThe vault of the sky.
3.nounOne of the celestial spheres of the Ptolemaic or geocentric model of the world."Aristotle makes [Fire] to move to the concave of the Moon. - Thomas Salusbury (1661)."
4.nounAn element of a curved grid used to separate desirable material from tailings or chaff in mining and harvesting.
5.nounAn indentation running along the base of a surfboard, intended to increase lift.
6.nounAn indented area on the top of a skateboard, providing a position for foot placement and increasing board strength.
7.verbTo render concave, or increase the degree of concavity.
8.adjectiveCurved like the inner surface of a sphere or bowl
9.adjective(of a polygon) not convex; having at least one internal angle greater than 180 degrees.
10.adjective(of a real-valued function on the reals) satisfying the property that all segments connecting two points on the function's graph lie below the function.
11.adjectiveHollow; empty