ball lightning

noun
a rare form of lightning, consisting of a bright, luminous ball that moves rapidly along objects or floats in the air.
Also called globe lightning.


Origin:
1855–60

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Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
ball lightning
 
n
meteorol a luminous electrically charged ball occasionally seen during electrical storms

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
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American Heritage
Science Dictionary
ball lightning  
A rare form of lightning in the shape of a glowing red ball, associated with thunderstorms and sometimes accompanied by a loud noise. Ball lightning is thought to consist of ionized gas.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

ball lightning

a rare aerial phenomenon in the form of a luminous sphere that is generally several centimetres in diameter. It usually occurs near the ground during thunderstorms, in close association with cloud-to-ground lightning. It may be red, orange, yellow, white, or blue in colour and is often accompanied by a hissing sound and distinct odour. It normally lasts only a few seconds, usually moving about and then vanishing suddenly, either silently or explosively. Ball lightning has been reported to cause damage by burning or melting but is usually harmless. Its causes and its relation to common lightning are not known, but among the suggested explanations are: air or gas behaving abnormally, high-density plasma phenomena, an air vortex containing luminous gases, and microwave radiation trapped within a plasma bubble. Sometimes bead lightning is mistaken for ball lightning. Bead lightning is most apparent when the current in a cloud-to-ground flash persists for an appreciable fraction of a second. In these cases, the luminosity also persists and the channel may have regions of enhanced luminosity that resemble a string of beads.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
People have reported seeing ball lightning-a rare phenomenon that resembles a glowing sphere of electricity-for hundreds of years.
Magnetohydrodynamic equilibrium of plasma ball lightning.
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