Plain English Meaning
A system that makes GPS more accurate and reliable for aircraft by sending small correction signals from ground stations through satellites to your GPS receiver, allowing precise approaches into airports.
Full Definition
A satellite-based augmentation system developed by the FAA that improves the accuracy, integrity, and availability of GPS signals over a wide geographic area. Ground reference stations monitor GPS satellite signals, calculate correction data, and uplink that data to geostationary satellites, which broadcast the corrections to suitably equipped aircraft receivers. WAAS supports , , and approaches with down to .