El-lip'soid, n.

n. [Fr. ellipsoïde, from Lat. ellipsis, Gr. ἔλλειψις, and εἶδος, form.] (Geom.) A solid figure, all plane sections of which are ellipses or circles.

Ellipsoid of revolution, a solid figure generated by the revolution of an ellipse about one of its axes. It is called a prolate ellipsoid when the ellipse is revolved about the major axis, and an oblate ellipsoid when it is revolved about the minor axis.