cassinoid

cassinoid Geom.

(ˈkæsɪnɔɪd)

[a. F. cassinoide: see cassinian and -oid.]

A curve which Cassini wished to substitute for the ellipse, in explanation of the planetary movements: an oval having two foci, such that the product of the focal radii of any point on the curve is constant (instead of their sum being constant as in the ellipse).