barycenter

from WordNet (r) 3.0 (2006)

barycenter
    n 1: (astronomy) the common center of mass around which two or
         more bodies revolve

from The Collaborative International Dictionary of English v.0.48

barycenter \barycenter\ n.
   the point representing the mean position of the matter in a
   body.

   Syn: centroid, center of mass.
        [WordNet 1.5]