The Collaborative International Dictionary of English v.0.48:
Polygonal \Po*lyg"o*nal\, a. Having many angles. [1913 Webster] Polygonal numbers, certain figurate numbers. See under Figurate. [1913 Webster]WordNet (r) 3.0 (2006):
polygonal adj 1: having many sides or relating to a surface marked by polygons; "polygonal structure"