What is a quadrigon?

A Quadrigon is a polygon of 4 points (no 3 of which are collinear) and 4 lines spanned between the 4 points in such a way that each line connects only 2 of the 4 points and each point is the intersection of just 2 of the 4 lines. This figure is also sometimes called a Tetragon.

See: http://chrisvantienhoven.nl/quadrigon-objects.html.