n. A large chunk of ice that forms in the atmosphere and falls to the ground.
A Spanish-American scientific team is monitoring ice events in the United States this winter following research on a baffling phenomenon first detected here.

They're not watching for ordinary ice storms or slick roads, but incidents involving "megacryometeors," great balls of ice that fall out of the clear blue sky - possibly due to global warming.
—Michael Woods, “Scientists try to crack the mystery of falling ice balls,” Toledo Blade, December 10, 2003
Megacryometeors are large chunks or blocks of ice that sail through the atmosphere, often clunking down on the surface. Jesus Martinez-Frias of the Astrobiology Center in Madrid has been monitoring these falling blocks of ice.
—Pat Shingleton, “Pat Shingleton's weather news,” The Advocate, January 22, 2003
2002 (earliest)
A team led by meteorologist Millan Millan, head of the Mediterranean Center for Environmental Studies in Valencia, has found that the lower stratosphere was unusually moist at the time the ice balls fell. Millan estimates that a "condensation aggregate"—a growing ice ball—would free-fall about 19 kilometers through a nearly saturated atmosphere. The roughly 10 minutes of free-fall would be enough time for kilogram-sized ice balls to form, Millan argues: "We appear to be looking at nuclei that have descended through a very moist atmosphere, growing as they fell." The source of the nuclei, Martinez-Frias and Travis suggest, could have been lingering jet contrails. Remnants of contrails can last for days as wispy cirrus clouds that are sometimes invisible to the naked eye. Many fewer nuclei would be available in these conditions than in a hail-forming thunderstorm, thus explaining why there were so few "megacryometeors" as Martinez-Frias calls the ice balls.
—Xavier Bosch, “Great balls of ice!,” Science, August 02, 2002
This mouthful of a word combines mega, "very large," cryo, "ice," and meteor, "a space rock that streaks through the earth's atmosphere." Isn't this just a fancy-schmancy word for "really big hail"? Probably, although we're talking, well, mega-hail. Your typical megacryometeor weighs in at roughly 25 to 35 pounds, and there have been reports of a 440-pound chunk that landed in Brazil a while back. Fortunately, most megacryometeors land harmlessly in remote areas, but they've been known to tunnel through roofs, obliterate car windshields, and come uncomfortably close to people's noggins. Michael Woods, author of the first example citation, reports that a block of ice described by eyewitnesses as "half the size of a car" punched through the roof of an automobile dealership in Lawrenceville, Georgia. Heads up!
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