Plain English Meaning
A loud, high whining sound coming through the headset or speakers, usually caused by static electricity building up on the aircraft and interfering with the radios.
Full Definition
A sharp, high-frequency whining or screeching noise heard through the aircraft's communication or navigation receivers, typically caused by precipitation static (P-static) — the buildup and discharge of static electricity on the airframe as the aircraft flies through precipitation, dust, or ice crystals.
Context Anchor
Seen in discussions of precipitation static, especially when flying near rain, snow, ice crystals, or dust that can create radio noise.