What does a flashing white light from the control tower indicate while taxiing?

A flashing white light from the control tower while taxiing is indeed an indication to return to the starting point. This signal is used to inform pilots that they should discontinue their current taxiing procedures and go back to their original location, usually the departure gate or ramp area.

This light is part of a series of optical signals that control towers utilize to communicate with aircraft when verbal communication may be impossible or less effective. It serves as a clear and unambiguous instruction for pilots, especially when there is a need to manage runway space or when there are changes in the flight operation status.

The other options do not align with what the flashing white light signifies. For example, takeoff and landing clearances are typically communicated through standard radio communications rather than light signals. Standby instructions would not require a flashing white light, as these would normally be communicated differently. Thus, the flashing white light specifically indicates that pilots should return to their starting position, making this the correct interpretation of the signal.