What is a 7-sided polygon with an interior right angle?

The equation for the size of an interior angle of an n-sided regular polygon is (n-2)180/n. When n=7, the interior angle of a regular sided shape would be 5x180/7 or approximately 128.57. The polygon in the question has an interior right angle (90 degree angle) and thus cannot be a regular shape. A 7 sided shape is called a heptagon. Thus, the shape described in the question is an irregular heptagon.