A heptagram or septegram is a seven-pointed star drawn with seven straight strokes.
In general, a heptagram is any self-intersecting heptagon (7-sided polygon

Polygon

In geometry a polygon is a flat shape consisting of straight lines that are joined to form a closed chain orcircuit.A polygon is traditionally a plane figure that is bounded by a closed path, composed of a finite sequence of straight line segments...

).

There are two regular heptagrams, labeled as {7/2} and {7/3}, with the second number representing the vertex interval step from a regular heptagram, {7/1}.

This is the smallest star polygon that can be drawn in two forms, as irreducible fraction

Irreducible fraction

An irreducible fraction is a vulgar fraction in which the numerator and denominator are smaller than those in any other equivalent vulgar fraction...

s.