Plain English Meaning
A specific radio channel that aircraft below 18,000 feet use to send their position and to receive free weather and traffic information from FAA ground stations.
Full Definition
A radio frequency channel operating at 978 megahertz, used by the Universal Access Transceiver (UAT) system to transmit and receive ADS-B traffic data, Flight Information Service-Broadcast (FIS-B) weather and aeronautical information, and -Broadcast () data between aircraft and ground stations. In the , the UAT is for use only by aircraft operating below 18,000 feet and is the channel that carries the free FIS-B weather products to suitably equipped aircraft.