concave — English Dictionary

Adjective

1. Curved like the inner surface of a sphere or bowl.

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

   Usage

   • not-comparable
   • of a polygon

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

   Usage

   • not-comparable
   • of a real-valued function on the reals

4. Hollow; empty.

   Examples

   as concave […] as a worm-eaten nut

Noun

1. A concave surface or curve.

2. The vault of the sky.

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

   Examples

   Aristotle makes [Fire] to move to the concave of the Moon. - Thomas Salusbury (1661).

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

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

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

7. A playing card made concave for use in cheating.

Verb

1. To render concave, or increase the degree of concavity.

Adjective

1. curving inward

   Antonyms

   convex