What is the meaning of Concave?

Curved like the inner surface of a sphere or bowl.

Not convex; having at least one internal angle greater than 180 degrees.

Satisfying the property that all segments connecting two points on the function's graph lie below the function.

Hollow; empty.

A concave surface or curve.

The vault of the sky.

One of the celestial spheres of the Ptolemaic or geocentric model of the world.

An element of a curved grid used to separate desirable material from tailings or chaff in mining and harvesting.

An indentation running along the base of a surfboard, intended to increase lift.

An indented area on the top of a skateboard, providing a position for foot placement and increasing board strength.

A playing card made concave for use in cheating.

To render concave, or increase the degree of concavity.

concave

feminine plural of concavo

vocative masculine singular of concavus

Source: wiktionary.org