Plain English Meaning
A radio-and-data system, used only in the United States and only below 18,000 feet, that lets an aircraft broadcast where it is and also receive free weather and traffic information from the ground.
Full Definition
A datalink system operating on 978 MHz used by ADS-B Out and ADS-B In equipment in U.S. airspace below 18,000 feet MSL. UAT broadcasts an aircraft's GPS-derived position, altitude, and identity to ATC and other aircraft, and can also receive Flight Information Service-Broadcast (FIS-B) weather products and -Broadcast () data.