The term "user agent" is commonly used in the web development world to describe the software or application that acts as an intermediary between the user and the browser. However, there are several synonyms for this term that can be used interchangeably. Some examples include "client," "browser agent," "client agent," "browser user agent," and "HTTP client." Each of these terms is used to describe the same concept - the software or application that identifies itself to the server when making requests. While the term "user agent" is still widely used, it's helpful to know the other synonyms and when they may be used in place of the original term.