Plain English Meaning
Weather information that's being read out continuously over a radio frequency. You tune in, listen, and get the current conditions without having to ask anyone.
Full Definition
Aviation weather information transmitted continuously or at scheduled intervals over radio frequencies, allowing pilots to receive current weather and aeronautical data in flight without requesting it from a controller or specialist. Common examples include ATIS at airports, AWOS and ASOS at smaller fields, and HIWAS for hazardous weather advisories along a route.
Context Anchor
Seen when studying how pilots get weather updates before flight or while airborne, especially in instrument flying.