Speed with which an aircraft traverses the ground over which it flies.
The speed of an aeroplane relative to the earth's surface, as distinct from its speed through the air. Thus if an aeroplane is flying at 200 m.p.h. through the air and is flying against a steady wind of 20 m.p.h. its ground speed will be 180 m.p.h.
The speed of an aircraft relative to the surface of the Earth, taking the influence of headwinds and tailwinds into account.