Meaning of center of mass

cen'ter of mass'

Pronunciation: [key]
— Mech. Mech.
  1. the point at which the entire mass of a body may be considered concentrated for some purposes; formally, the point such that the first moment of a physical or geometric object about every line through the point is zero. Cf. moment (def. 8).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.