metacentre

1. (physics, nautical) The point where a vertical line through a tilted vessel's center of buoyancy intersects the originally-vertical (but-now-tilted) line that passed through the center of buoyancy when the vessel was upright; it must be above the vessel's center of gravity for the vessel to have positive static stability (to tend to return to an upright orientation if rolled to one side, rather than to continue rolling to an inverted orientation).Examples: "A ship's metacenter (M) is the virtual intersection of two successive lines of action of the force of buoyancy when the ship heels through a very small angle. The initial position of the metacenter is used as a reference in stability calculations. The distance from a ship's center of gravity (G) to its metacenter is known as the metacentric height (GM). GM is a measure of the vessel's ability to right itself when experiencing an overturning moment. For the same vessel, a higher GM value indicates a greater initial static stability."