'Concavity' definitions:

Definition of 'concavity'

(from WordNet)
noun
A shape that curves or bends inward [syn: concave shape, concavity, incurvation, incurvature]
noun
The property possessed by a concave shape [syn: concavity, concaveness]

Definition of 'Concavity'

From: GCIDE
  • Concavity \Con*cav"i*ty\, n.; pl. Concavities. [L. concavitas: cf. F. concavit['e]. See Concave.] A concave surface, or the space bounded by it; the state of being concave. [1913 Webster]