[di.rec.trix] n, pl -trix.es also -tri.ces [ML, fem. of LL director, fr. L dirigere] (1622) 1 archaic: directress
2: a fixed curve with which a generatrix maintains a given relationship in generating a geometric figure; specif: a straight line the distance to which from any point of a conic section is in fixed ratio to the distance from the same point to a focus