Plain English Meaning
A set of automatic weather instruments at an airport that measure the local weather and read it out loud over the radio so pilots can hear the current conditions before landing or taking off.
Full Definition
A ground-based system of sensors installed at or near an airport that automatically measures local weather conditions — such as wind speed and direction, visibility, cloud height, temperature, dew point, and altimeter setting — and broadcasts the information continuously over a dedicated or telephone line.