metacentre

Meaning

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).