The Collaborative International Dictionary of English v.0.48:

Sphericity \Sphe*ric"i*ty\, n. [Cf. F. sph['e]ricit['e].]
   The quality or state of being spherial; roundness; as, the
   sphericity of the planets, or of a drop of water.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sphericity
    n 1: the roundness of a 3-dimensional object [syn: sphericity,
         sphericalness, globosity, globularness, rotundity,
         rotundness]