Geoidal

[jee-oid] /ˈdʒi ɔɪd/

noun
1.
an imaginary surface that coincides with mean sea level in the ocean and its extension through the continents.
2.
the geometric figure formed by this surface, an ellipsoid flattened at the poles.
/ˈdʒiːɔɪd/
noun
1.
a hypothetical surface that corresponds to mean sea level and extends at the same level under the continents
2.
the shape of the earth
geoid
(jē’oid’)
The hypothetical surface of the Earth that coincides everywhere with mean sea level and is perpendicular, at every point, to the direction of gravity. The geoid is used as a reference surface for astronomical measurements and for the accurate measurement of elevations on the Earth’s surface.