The “bomb cyclone” about to wallop the East Coast has been referred to as a bombogenesis by meteorologists — leaving many scratching their heads. It’s also left Americans still digging themselves out of a foot or more of snowfall from last weekend’s Winter Storm Fern, worrying about being buried by another few inches.

The largest nontropical bomb cyclone on record since 1958 struck over the northern Pacific Ocean on New Year’s Eve from 2020 into 2021.

A bomb cyclone, also known as bombogenesis, happens when a mid-latitude storm system strengthens very quickly, usually over the course of about 24 hours. According to the National Oceanic and Atmospheric Administration, this rapid shift is marked by a sharp drop in air pressure.