What exactly is a “bomb cyclone?”
The ominous name "bomb cyclone" comes from a process called explosive cyclogenesis, or bombogenesis, in which a weather system undergoes a rapid drop in pressure.
Bombogenesis occurs "when a midlatitude cyclone rapidly intensifies, dropping at least 24 millibars over 24 hours," according to the National Oceanic and Atmospheric Administration (NOAA).
A millibar measures atmospheric pressure. A drop in pressure in a system equals strengthening of the system.
Think of it as a winter hurricane.
Such weather systems in the northern hemisphere are centers of low pressure. When the pressure drops, the storms get stronger. When they drop in such a dramatic fashion over a short period of time, the results are equally dramatic.