mediatrix

noun2

1. •
   A female mediator.

   • He promised, however, to speak to Mr. Harrel upon the subject, but the promise was evidently given to oblige the fair mediatrix, without any hope of advantage to the cause. — 1782
2. •
   (rare) A bisector, the line that is perpendicular to a line segment and intersects the line segment at its midpoint.

   • […] the intersection of the normal at M to the parabola with the mediatrix of the line […] — 2000