adj, noun, verb ·Common ·High school level

Definitions

Noun

1. 1
   A concave surface or curve.
2. 2
   The vault of the sky.
3. 3
   One 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. 4
   An element of a curved grid used to separate desirable material from tailings or chaff in mining and harvesting.
5. 5
   An indentation running along the base of a surfboard, intended to increase lift.

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6. 6
   An indented area on the top of a skateboard, providing a position for foot placement and increasing board strength.
7. 7
   A playing card made concave for use in cheating.

Verb

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

Adjective

1. 1
   Curved like the inner surface of a sphere or bowl.
2. 2
   Not convex; having at least one internal angle greater than 180 degrees. not-comparable
3. 3
   Satisfying the property that all segments connecting two points on the function's graph lie below the function. not-comparable
4. 4
   Hollow; empty.

   "as concave […] as a worm-eaten nut"

Adjective

1. 1
   curving inward wordnet

Synonyms

All synonyms

acetabularalveolusarchedarciformarclikearcual

Antonyms

All antonyms

convexnonconcave

Example

More examples

"The moon's orbit is always concave toward the sun."

Etymology

From Middle English concave, from Old French concave, from Latin concavus.

Related phrases

concave envelopeconcave functiondouble concaveupper concave envelope

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.