dirigent

1. (now chiefly biochemistry) Something that or someone who directs; a director or guide.Examples: "The monolignol substrates are held in position by proteins called dirigents (guide proteins).[…]Lignan dirigent proteins are found in the cytoplasm, but similar dirigents have been localized in the cell walls of some plants."; "One of its members is deputed in rotation to maintain continuous contact with the director or dirigents of the hospital by means of biweekly, if necessary daily, visits to the institution."

2. (dated, geometry) The line of motion of a describent line or surface that in so moving defines a plane or solid figure; a directrix.Examples: "The straight line in which the vertical polar plane cuts the plane of the circle of contact is called the dirigent. As there are in general two circles of contact, there are two dirigents, and they are parallel to the diretrices."; "In this case, to which Sphero-Cartesians, and all other sphero-quadrics, whose dirigents are small circles, are analogous in Spherics, the dirigent conic F must also have double contact with S."dated