Tschirnhausen's cubic

Tschirnhausen's cubic

[′chərn‚hau̇z·ənz ′kyü·bik]
(mathematics)
A plane curve consisting of the envelope of the line through a variable point P on a parabola which is perpendicular to the line from the focus of the parabola to P. Also known as l'Hôpital's cubic; trisectrix of Catalan.