directrices

/D ER0 EH1 K T R IH0 S IH0 Z/
noun
  1. 1

    A female who directs; a directress.

  2. 2

    A line used to define a curve or surface; especially a line, the distance from which a point on a conic has a constant ratio to that from the focus.

Source: https://en.wiktionary.org/wiki/directrices, https://en.wiktionary.org/wiki/directrix