n. a line around which a geometric figure is symmetrical, in that for every point P of the figure there is another, P', such that the perpendiculars from the two points to the line are coincident and of equal length. For example, a regular hexagon has six axes of symmetry, namely all the bisectors of its angles and sides; the graph of cos(x), as shown in has the y-axis as an axis of symmetry. Compare center of symmetry.