Noun
pyrocumulus (plural pyrocumuli)
(volcanology, meteorology) A dense cloud associated with fire or volcanic activity.
“Eventually,” says Smith, “when that pyrocumulus reaches 40,000 feet or so, it cools, loses its buoyancy, and then drops in downdrafts 40 miles an hour straight into the canyons, blowing fire everywhere. Source: Internet
The ominous cloud formation is known as a pyrocumulus cloud. Source: Internet