righting arm

Noun

 * 1)  The horizontal distance between the center of mass of a tilted vessel and the vertical line connecting its center of buoyancy and its metacentre (conventionally taken as positive if the aforementioned line lies on the low side of the center of mass, and negative if the line lies on the high side of the center of mass), measuring the strength of the vessel's tendency (or lack thereof) to return to an upright orientation.