: a form of electrical discharge that is emitted upward from the top of a cumulonimbus cloud during a thunderstorm and that usually appears as a very short-lived reddish circle of light
"Elves" appear as rapidly expanding doughnuts of light that vanish in less than a millisecond. They most likely result when an electromagnetic pulse from an energetic cloud-to-ground lightning strike propagates into the ionosphere. While elves may accompany sprites, the mechanisms that create the two differ.—
Stephen James O'Meara, Astronomy, June 2010
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Merriam-Webster unabridged
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