centroid

from WordNet (r) 3.0 (2006)

centroid
    n 1: the center of mass of an object of uniform density

from The Collaborative International Dictionary of English v.0.48

Centroid \Cen"troid\ (s[e^]n"troid), n. [L. centrum + -oid.]
   The center of mass, inertia, or gravity of a body or system
   of bodies.
   [1913 Webster]