What does "taxi" refer to in aviation terms?

In aviation terms, "taxi" refers specifically to the movement of an aircraft on the ground. This includes the actions of an aircraft when it is not airborne, such as moving from the gate to the runway before takeoff, or from the runway back to the gate after landing. This movement is performed on taxiways and runways and is an essential part of the flight process, ensuring that aircraft are safely maneuvered in congested airport environments.

The significance of this term centers around ground operations, which are crucial for airport safety and efficiency. While the other options relate to different phases of flight, such as taking off or descending, they do not capture the unique aspect of an aircraft's ground movement that "taxi" describes. Therefore, understanding the term "taxi" is vital for comprehending airport operations and the sequence of events that occur before and after flying.