oblate spheroid prolate spheroid A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. Three particular cases of a spheroid are: If the ellipse is rotated about its major axis, the surface is a prolate spheroid (similar to the shape of a rugby ball). If the ellipse is rotated about its minor axis, the surface is an oblate spheroid (somewhat similar to the shape of the planet Earth). If the generating ellipse is a circle,… (More on Spheroid)