ellipsoid

A surface, all of whose cross sections are elliptic or circular (including the sphere), that generalises the ellipse and in Cartesian coordinates (x, y, z) is a quadric with equation x2/a2 + y2/b2 + z2/c2 = 0.

Such a surface used as a model of the shape of the earth.

“Here the geoid is thirty meters below the ellipsoid.”

Shaped like an ellipse; elliptical.

Of or pertaining to an ellipse; elliptic.

Having the tridimensional shape of an ellipse rotated on its long axis.