hexagram

WordNet 3.6
 n hexagram a regular polygon formed by extending each of the sides of a regular hexagon to form two equilateral triangles
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Webster's Revised Unabridged Dictionary

 n Hexagram A figure of six lines
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Century Dictionary and Cyclopedia

 n hexagram A figure formed of two equilateral triangles placed concentrically with their sides parallel and on opposite sides of the center. This was the seal or symbol of the Pythagorean school.
 n hexagram In geometry, a figure of six lines. The name is particularly applied to the mystic hexagram invented by Pascal. This is a hexagram inscribed in a conic. It has the property that the intersections of the first and fourth, the second and fifth, and the third and sixth lines lie on one straight line. This is a case of the elementary proposition that three cubic curves which have eight points in common also have a ninth in common. Brianchon's hexagram is circumscribed about a conic; and the chief property of it is that the three lines joining opposite angles intersect in one point.
 n hexagram In Chinese lit, one of the 64 figures which form the basis of the Yihking or “book of changes,” one of the oldest Chinese books. Each of these figures is made up of six parallel lines, of which some are whole and some divided. See book of changes, under change.
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Webster's Revised Unabridged Dictionary
Hexa, + gram,
In literature:
The hexagram at ten years old would be a hundred times less unlikely.
"A Budget of Paradoxes, Volume I (of II)" by Augustus De Morgan
Pascal's Hexagram, I, 221.
"A Budget of Paradoxes, Volume II (of II)" by Augustus de Morgan
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