Plume
Plume turns up in 2 fields: thermal spray, nuclear. Here is what it means to the people in each one.
Plume in thermal spray
The visible jet of hot gas and glowing particles streaming from the spray gun toward the part.
Luminous jet leaving a plasma, HVOF or flame gun, with the powder stream visible as a brighter trail inside it. Experienced sprayers read the plume's color, length, shape and stability for problems: a flickering plume points to pulsing feed, a stream that veers off the axis means bad injection, and visible shock diamonds in an HVOF jet show supersonic flow.
"Look at the plume, the powder's riding the top edge, the injector must have shifted on the gun."
Plume in nuclear
The cloud of radioactive gases and particles carried downwind from a release.
The airborne mass of radioactive material moving and spreading with the wind after a release. People near it receive external dose from the cloud itself (cloudshine), from material deposited on the ground (groundshine) and internal dose by inhalation. Emergency planners track the plume's direction by sector and its arrival time, and field monitoring teams try to find its edges and centreline.
"Wind's out of the southwest at 8 miles an hour, plume should reach sector N by 1430."