(geometry) A cyclic hexagon with vertices given by the six intersections of the edges of a triangle and the three lines that are parallel to the edges that pass through its symmedian point.

plural of Lemoine hexagon

(geometry) A nonplanar hexagon whose three diagonals meet.

plural of Brianchon hexagon

(astronomy) An asterism with vertices at Rigel, Aldebaran, Capella, Pollux, Procyon, and Sirius.