Cĭs'soid, n.

n. [Gr. κισσοειδής, like ivy, from κισσός, ivy, and εἶδος, form.] (Geom.) A curve invented by Diocles, for the purpose of solving two celebrated problems of the higher geometry; viz., to trisect a plane angle, and to construct two geometrical means between two given straight lines. Math. Dict.