Which term describes a transportation system where a vessel travels from Point A to B to C to D and returns to A?

The term that accurately describes a transportation system where a vessel travels sequentially from Point A to B to C to D and then returns to Point A is a "Circular Route." This concept encapsulates the essence of a route that forms a circle, allowing the vessel to return to its original starting point after visiting a series of predetermined locations.

In contrast, the term "Point to Point" typically refers to a service that connects two specific locations directly without making intermediate stops, which does not align with the described sequential travel. Additionally, "Linear Route" describes travel along a straight path between two points, likely without the circular return. The term "Hub and Spoke" is more associated with a central hub that connects to various destinations directly from it, which does not fit the continuous circular pattern indicated in the question. Thus, "Circular Route" is the precise terminology reflecting this type of travel scenario.