Source : Webster's Revised Unabridged Dictionary (1913)

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}.