The best replacement for polygon is non polygon.

The best alternatives to polygon are rated as following:
★★★★★  non polygon
★★★★  polyhedron
★★★★  regular polygon
★★★★  histogram
★★★★  nurbs
★★★  quadrilateral
★★★  not a polygon
★  bar graph
★  line graph
★  kotaku
★  ogive
★  polyline
★  voxel
★  irregular polygon
★  nurbs modeling
★  polygon
★  pentagon
★  hexagon
  polygonal region
  multipolygon
  trapezoid
  not polygon
  low polygon
  histograms

Your alternative for polygon is not listed? Suggest!
Speaking about polygon, one probably shouldn't forget about right angles.

Other search terms related to polygon and their ratings are:
★★★★★ right angles
★★ equal sides
★ histogram
You have in mind a companion for polygon and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of polygon in all years. Click on graph for more.
polygon
non polygon
polyhedron