The Collaborative International Dictionary of English v.0.48:

Quadratrix \Quad*ra"trix\, n.; pl. -trixes, or -trices.
   [NL.] (Geom.)
   A curve made use of in the quadrature of other curves; as the
   quadratrix, of Dinostratus, or of Tschirnhausen.
   [1913 Webster]