Which term refers to the designated area surrounding a holding pattern where no unwanted traffic should enter?

The term that refers to the designated area surrounding a holding pattern where no unwanted traffic should enter is "protected airspace." This concept is crucial in aviation to ensure that flight operations can proceed safely without interference from other aircraft. Protected airspace is established to create a safe buffer around the holding pattern, allowing pilots to perform maneuvers without the risk of conflicting with other aircraft that may be in the vicinity.

In contrast, while a buffer zone is a similar concept that suggests a protective area, it is not the specific term used in aviation terminology for holding patterns. Controlled airspace refers to airspace where flight operations are regulated and require specific permissions or communication with Air Traffic Control, but it does not specifically denote the area surrounding a holding pattern. A safety corridor usually suggests a designated route or area for safe travel, but does not specifically apply to the context of holding patterns. Hence, "protected airspace" is the most accurate term in this context.