noun, plural fly·bys.
- the flight of a spacecraft close enough to a celestial object, as a planet, to gather scientific data.
- Aeronautics.
- Also called flypast.a low-altitude flight of an aircraft for the benefit of ground observers.
- flyover(def 1).
noun plural -bys
- a flight past a particular position or target, esp the close approach of a spacecraft to a planet or satellite for investigation of conditions