The Collaborative International Dictionary
Generatrixes
Generatrix \Gen`er*a"trix\, n.; pl. L. Generatrices, E. Generatrixes. [L.] (Geom.) That which generates; the point, or the mathematical magnitude, which, by its motion, generates another magnitude, as a line, surface, or solid; -- called also describent.
Wiktionary
generatrixes
n. (plural of generatrix English)