Definition
The release of accumulated electrical charge from a body, occurring when the built-up voltage exceeds the surrounding air's ability to insulate it. On an aircraft, this happens as static electricity collected on the airframe escapes into the surrounding air, often as a small spark or a continuous flow of charge from sharp points or trailing edges.
Plain English
Static that has built up on the airplane gets released back into the air. Once the charge is large enough, it has to go somewhere -- so it leaks or jumps off the aircraft.
Context Anchor
Seen in discussions of precipitation static, especially when rain, snow, ice crystals, or dust cause electric charge to build up on the aircraft and interfere with radios or navigation receivers.
Derivation
Discharge' comes from the Old French 'descharger,' meaning 'to unload.' The aircraft has been 'loaded' with electrical charge from friction with precipitation, and the discharge is simply the unloading of that charge back into the air.
Why Pilots Care
Unmanaged electrical discharge produces broadband radio noise that can mask ATC communications and navigation signals, and in severe cases may damage antennas or composite structures.
Analogy
It is like the small shock you may feel after walking across carpet and touching a metal doorknob. Charge built up on you, then quickly moved to the doorknob when it found a path.
Grounding Statement
Think of flying through snow and watching tiny sparks trail off the wingtips at night -- that visible spark is the airframe shedding the charge it built up by friction with the precipitation.
Intuition Check
Electrical discharge does not always mean lightning. Here, it can mean smaller releases of static electricity from the aircraft into the air.
Example Sentence 1
Flying through heavy snow, the crew noticed loud crackling on the VHF radio caused by electrical discharge from the airframe.
Example Sentence 2
Bonding straps are installed to provide a controlled path for any electrical discharge and reduce radio interference.