Plain English Meaning
A landing system that uses GPS, but with a local airport ground station that fixes small GPS errors and sends the corrections to the aircraft so it can fly an accurate approach down to the runway.
Full Definition
A precision approach and landing system that uses GPS signals corrected and enhanced by a Ground-Based Augmentation System (GBAS) located at or near the airport. A GBAS ground station receives GPS signals, calculates correction data, and broadcasts it via VHF data link to aircraft on approach, allowing them to fly precision approaches with vertical and lateral guidance comparable to an .