What does "hexagram" mean?

Hexagram: (a) A figure composed of two equal triangles intersecting so that each side of one triangle is parallel to a side of the other, and the six points coincide with those of a hexagon. (b) In Chinese literature, one of the sixty-four figures formed of six parallel lines (continuous or broken), forming the basis of the Yih King, or "Book of Changes." S. W. Williams.