What term describes a clause that prevents an employee from joining a rival company or starting their own?

The correct term that describes a clause preventing an employee from joining a rival company or starting their own is a non-compete agreement. This agreement is specifically designed to restrict employees from engaging in business activities that directly compete with their employer after the employment relationship ends.

A non-compete agreement typically outlines the duration and geographic scope in which the employee is prohibited from competing. It aims to protect the employer's business interests, trade secrets, and client relationships. While "restraint of trade" is a broader legal principle that encompasses various agreements limiting business competition, it is not the specific term used to define an agreement designed to prevent employees from entering into competition with their former employers.

The other options—confidentiality clause and exclusivity agreement—serve different purposes. A confidentiality clause protects sensitive information from being disclosed, while an exclusivity agreement ensures that parties involved in a contract will only deal with each other, rather than engaging with others in competing interests.