blue jet

noun

Definition of blue jet

: a rare form of electrical discharge that is emitted from the top of a cumulonimbus cloud during a thunderstorm as a large upward jet of blue light Wescott and Sentman discovered that sprites are salmon-colored, and as they flew with Tobolski over the Arkansas storm that summer, they discovered that sprites were not alone above the clouds: fountains of blue light emerged directly from the clouds as well. These they named blue jets.— Elwood Norris, Discover, July 1997 Blue jets, by far the rarest member of the menagerie, shoot up from cloudtops at speeds of more than 60 miles a second to heights of 30 miles.— Karen Wright, Scientific American, Spring 2000