The term Wagon Train Puller can be summarized as a job description for a MULE, which is a four-letter word. A MULE is an animal that is used to pull wagons in a wagon train, which is a group of wagons that travel together. The MULE is usually harnessed to the wagon and is responsible for providing the power to move the wagon forward. This job requires strength and endurance, as the MULE must be able to pull the wagon for long distances.