A more thorough explanation:

Definition: Third-party practice is a legal procedure where a defendant brings in a third party to a lawsuit, usually to shift liability to someone not sued by the plaintiff. This is also known as impleader or vouching-in.

Example: If a person is sued for a car accident, they may use third-party practice to bring in the car manufacturer or mechanic who worked on the car as a third party. The defendant may argue that the accident was caused by a defect in the car or by the mechanic's negligence, and therefore, they should not be held solely responsible for the damages.

This example illustrates how third-party practice can be used to shift liability to someone else who may have contributed to the plaintiff's damages.