Plain English Meaning
A pilot report describing dangerous weather a pilot has actually encountered. These reports are passed along right away because other pilots in the area need to know straight away.
Full Definition
A category of pilot weather report (PIREP) used to relay weather conditions considered hazardous to flight, including tornadoes, funnel clouds, waterspouts, severe or extreme turbulence, severe icing, hail, low-level wind shear, volcanic ash, or any other weather phenomenon reported that is considered hazardous or potentially hazardous. Urgent PIREPs are transmitted by and upon receipt and are designated with the prefix .