What is "geopotential height"

n. The height above sea level of a given pressure in the atmosphere

Geopotential height is a vertical coordinate referenced to Earth's mean sea level — an adjustment to geometric height ( elevation above mean sea level) using the variation of gravity with latitude and elevation. Thus it can be considered a "gravity-adjusted height". One usually speaks of the geopotential height of a certain pressure level, which would correspond to the geopotential height necessary to reach the given pressure.