What is "skew polygon"

In geometry, a skew polygon is a polygon whose vertices are not all coplanar. Skew polygons must have at least 4 vertices. The interior surface (or area) of such a polygon is not uniquely defined.

Skew infinite polygons (apeirogons) have vertices which are not all collinear.

A zig-zag skew polygon or antiprismatic polygon has vertices which alternate on two parallel planes, and thus must be even-sided.

Regular skew polygon in 3 dimensions (and regular skew apeirogons in 2 dimensions) are always zig-zag.