Plain English Meaning
A non-stop weather warning broadcast pilots can listen to over certain navigation radio stations while flying. It tells them about dangerous weather happening in their area without them needing to call anyone.
Full Definition
A continuous broadcast of recorded hazardous weather information transmitted over selected VOR (VHF Omnidirectional Range) navigation frequencies. The broadcast contains summaries of current weather hazards such as severe weather warnings, SIGMETs, Convective SIGMETs, AIRMETs, urgent pilot reports, and Center Weather Advisories affecting the within roughly 150 of the broadcasting .