A "bomb cyclone" sounds terrifying. And it looks fairly terrifying, too, if the spectacular pictures of the snow and other weather hitting the US are anything to go by.

But what really is the bizarre weather event that's sweeping over the US? And why is it a bomb?

The name comes from a very real weather term that refers to the kind of storm that formed itself off the southeast coast of the US. And the danger that it gives off is accurate, with the storm leading to high winds and some snow.

Heavy snowfall across Britain: in pictures Show all 18 1 /18 Heavy snowfall across Britain: in pictures Heavy snowfall across Britain: in pictures A snowplough clears a closed road on the A470 from Merthyr Tydfil to Brecon PA Heavy snowfall across Britain: in pictures Pedestrians walk over the Millennium Bridge with St Paul's Cathedral pictured in the background as snow falls AFP/Getty Images Heavy snowfall across Britain: in pictures Snow in Wood Green Rex Features Heavy snowfall across Britain: in pictures People walk through the snow in a park in north London EPA Heavy snowfall across Britain: in pictures Two girls make a snowman on Primrose Hill PA Heavy snowfall across Britain: in pictures People wake up to a blanket of overnight snowfall in Stoke On Trent Getty Images Heavy snowfall across Britain: in pictures Harlequins win a line-out in heavy snow during the European Rugby Champions Cup match against Ulster Rugby at Twickenham Stoop Getty Images for Harlequins Heavy snowfall across Britain: in pictures A train travels along snow covered tracks in High Wycombe EPA Heavy snowfall across Britain: in pictures Families take to the hills with sledges near Edale in Derbyshire AFP/Getty Images Heavy snowfall across Britain: in pictures People push a car up a snowy hill in north London EPA Heavy snowfall across Britain: in pictures A crashed lorry on the A50 is tended to by police as the snow falls near Uttoxeter REUTERS Heavy snowfall across Britain: in pictures People go sledding on Primrose Hill PA Heavy snowfall across Britain: in pictures Motorists brave the snow in Worcester PA Heavy snowfall across Britain: in pictures An abandoned car on the roadside on the Snake Pass in the Peak District PA Heavy snowfall across Britain: in pictures Heavy snow falls on sheep in the hills near Sennybridge, Wales REUTERS Heavy snowfall across Britain: in pictures Snow falling on Westminster Bridge Rex Features Heavy snowfall across Britain: in pictures Walkers on The Long Walk at Windsor PA Heavy snowfall across Britain: in pictures Motorist braves snowy conditions on the M2 motorway near Gillingham PA

But the cyclone isn't actually a bomb, obviously, and it doesn't have any of the explosiveness or immediacy that you'd expect from such a word.

Meteorologists have used the term "bomb" for storms for decades, based on a strict definition, said University of Oklahoma meteorology professor Jason Furtado.

After it showed up in a Washington Post story on Tuesday, the weather geek term took on a life of its own on social media. The same thing happened four years ago with "polar vortex," another long-used weather term that was little known to the public until then.

"Bombogenesis is the technical term. Bomb cyclone is a shortened version of it, better for social media," said Weather.US meteorologist Ryan Maue, who helped popularize polar vortex in 2014.

"The actual impacts aren't going to be a bomb at all," Maue said. "There's nothing exploding or detonating."

Storm intensity is measured by central pressure — the lower the pressure, the stronger. A storm is considered a "bomb" when the pressure drops rapidly — at least 24 millibars in 24 hours.

This storm has dumped freak snow on the Southeast, and all the way up the coast to Maine, and delivered near hurricane-force blistering winds. It will also usher in possible record-breaking cold.

Bomb cyclones draw air from polar regions after they leave. In this case, it means extra cold Arctic air because of where the polar vortex is, Furtado said.

Worldwide, about 40 to 50 "bomb cyclones" brew each year, but most are over open ocean and nobody but weather geeks notice, Maue said.

"We use the term bomb," Furtado said. "We know what it means, but I do think it gets a little hyped up."