Heptagonal
Heptagonal , adjective
[Compare French heptagonal.]
Having seven angles or sides.
Collocations (1)
Heptagonal numbers (Arithmetic) , the numbers of the series 1, 7, 18, 34, 55, etc., being figurate numbers formed by adding successively the terms of the arithmetical series 1, 6, 11, 16, 21, etc.