What does Leg Opening mean?
The opening at the bottom of denim, which varies depending on the style of jeans.
Heddels explains Leg Opening
The leg opening of a pair of jeans refers to the width of the cuff, or very bottom, of the jeans. For example, boot cut jeans have an average leg opening of 20”, while skinny jeans have a leg opening ranging from 10” to 14”.
Here is a picture of the leg opening: