Taxi
Manoeuvring on the ground under the aircraft's own power. The phase where runway incursions happen. Pushback and towing are recorded as Ground, not Taxi.
A runway incursion, meaning an aircraft, vehicle or person on a runway without clearance, is the ground counterpart to a mid-air collision, and it has produced the deadliest accident in aviation history. Investigations look at signage, lighting, low-visibility procedures, controller workload and readback discipline.
Movement under a tug, whether pushback from the gate or a repositioning tow, is not taxiing: the crew is not controlling the aircraft and the hazards belong to the ramp rather than the manoeuvring area. Those occurrences sit under Ground.