Dī-rĕc'trix, n.

n. [Fr. directrice, It. direttrice.]

1. A female who governs or directs.
2. (Geom.) (a.) A line along which a point in another line moves, and which governs its motion and determines the position of the curve generated by it, or along which the generatrix moves in generating a warped or single curved surface. (b.) A straight line so situated with respect to a conic section that the distance of any point of the curve from it has a constant ratio to the distance of the same point from the focus. In a parabola the directrix cuts the axis at right angles at a point just twice as far from the focus as the vertex. Math. Dict.