Action Over Exclusion

The International Risk Management Institute (IRMI) defines
third-party-over action as:
“A type of action in which an injured employee, after collecting workers’ compensation benefits from the employer, sues a third party for contributing to the employee's injury. Then, because of some type of contractual relationship between the third party and the employer, the liability is passed back to the employer by prior agreement. Depending on the nature and allegations of the action, coverage may be afforded under the contractual liability section of the employer's commercial liability policy or the employers’ liability section of the employer's workers’ compensation policy.”

For examples look at this article