Plain English Meaning
A way for pilots to receive weather updates while flying, sent wirelessly to a screen in the cockpit so they can see what the weather is doing without having to call anyone on the radio.
Full Definition
A cockpit service that delivers near real-time weather information to the aircraft in flight via a digital radio link, typically displayed on a multifunction display or portable electronic device. Common products include radar imagery, METARs, TAFs, AIRMETs, SIGMETs, winds aloft, and lightning data, transmitted through systems such as FIS-B (free, via ADS-B ground stations) or satellite-based services like SiriusXM .