directrix
di·rec·trixnoun
pl. -·trixes or -·tri·ces·- Rare a woman director
- Geom.
- a fixed line associated with a conic section and its focus and eccentricity
- the curve that bounds the base of a cone or cylinder
directrix
noun
pl. di·rec·trix·es, or di·rec·tri·ces- Mathematics A fixed curve traversed by a generatrix in generating a conic section or a cylinder.
- The median line in the trajectory of fire of an artillery piece.