What is "generatrix"

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.

n. (context geometry English) A curve that, when rotated about an axis, produces a solid figure

In geometry, a generatrix or generator is a point, curve or surface that, when moved along a given path, generates a new shape. The path directing the motion of the generatrix motion is called a directrix.