Definition
Directions issued by air traffic control (ATC) telling a pilot how to move an aircraft on the ground between the parking area, runways, and other points on the airport. Taxi instructions specify the route to follow, including the taxiways to use, any runways to cross or hold short of, and the destination point. Pilots are required to read back taxi instructions, particularly any hold-short or runway crossing clearances.
Plain English
The step-by-step directions ATC gives a pilot for driving the aircraft around the airport on the ground -- which paths to follow, where to stop, and where to end up.
Context Anchor
Pilots receive taxi instructions before moving from parking to the runway, after landing, and any time they need to move the aircraft on an airport surface under control.
Derivation
Taxi' in aviation comes from early aircraft moving slowly on the ground like a taxicab picking up or dropping off passengers. The term stuck and now means any ground movement of an aircraft under its own power.
Why Pilots Care
Prevents runway incursions and collisions with other aircraft or vehicles while moving on the ground.
Intuition Check
Taxi instructions are not casual suggestions. They are specific directions for ground movement, and if any part is unclear, the pilot should ask before moving.
Example Sentence 1
After starting the engine, the pilot called ground control and received taxi instructions to runway 27 via taxiways Alpha and Bravo, holding short of runway 18.
Example Sentence 2
Ground control issued new taxi instructions after the original route was closed for construction.