Definition
The portion of a takeoff or landing during which the airplane is in contact with the runway surface, rolling on its wheels. On takeoff, ground roll is the distance traveled from brake release until the wheels leave the runway. On landing, it is the distance from touchdown until the airplane comes to a stop or exits the runway.
Plain English
The part of a takeoff or landing where the airplane is still on its wheels, rolling along the runway, before it lifts off or after it touches down.
Context Anchor
Seen in takeoff and landing discussions, especially when judging how much runway the airplane will need.
Derivation
Ground means the surface under the airplane. Roll originally means to move by turning over, like a wheel. In this term, roll means the wheels are moving along the runway, not that the airplane is banking in flight.
Why Pilots Care
It determines the runway length needed for safe operations and directly affects go/no-go decisions in short-field or high-density-altitude conditions.
Intuition Check
Do not confuse ground roll with the airplane rolling left or right in flight. Here, roll means the airplane is moving along the runway on its wheels.
Example Sentence 1
With a heavy load and a hot day, the pilot calculated a ground roll of 1,400 feet before liftoff.
Example Sentence 2
A headwind shortened the ground roll by allowing the airplane to reach rotation speed sooner.