What does the term "bump" refer to regarding passengers?

The term "bump" specifically refers to the process of removing a passenger from a flight, often due to factors like weight and balance requirements or overbooking situations. Airlines sometimes sell more tickets than available seats, and when the flight is overbooked, they may need to "bump" a passenger to ensure the safety and operational efficiency of the flight. This action is generally taken so that the airline can comply with regulations and maintain balance during takeoff and flight. Passengers who are bumped usually have the option to receive compensation or rebooked on a later flight, making it a necessary practice in the airline industry.

In contrast, the other choices relate to different scenarios that do not capture the essence of the term in the context of airline procedures. For instance, upgrading a passenger's seat class involves enhancing their travel experience rather than removing them from a flight. Delaying a boarding time and assigning a passenger a different flight both pertain to changes in travel plans rather than the act of bumping someone from a flight entirely.