Plain English Meaning
Cockpit equipment that shows the pilot where thunderstorms are so they can be flown around rather than through.
Full Definition
Airborne instruments that locate and display thunderstorm activity relative to the aircraft, primarily airborne weather radar (which detects precipitation by reflecting radio energy off water droplets) and lightning detection systems such as a Stormscope or Strikefinder (which sense the electrical discharges produced by thunderstorms). These tools help the pilot identify, avoid, or circumnavigate convective weather.