centre of gravity

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics a point, near or within a body, through which its weight can be assumed to act when considering forces on the body and its motion under gravity. This coincides with the centre of mass in a uniform gravitational field
• noun any pivotal or central idea or group.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the point within something at which gravity can be considered to act; in uniform gravity it is equal to the center of mass