There are various synonyms for the term "stirrup iron," which is a piece of equipment used for horse riding. It's a crucial part of the saddle that provides support and balance to the rider. The most common synonyms for stirrup iron are stirrup, stirrup leather, and stirrup bar. Other words such as foot-iron and stirrup strap are also used interchangeably with stirrup iron. These synonyms are used to describe the same component of the saddle, which connects the stirrup leather to the saddle itself. Therefore, it's important to understand these terms and their usage in the equestrian world.