A plume is a visible smoke-like structure, which may contain pollutants emitted from an exhaust or smoke stack and released into the atmosphere. This elongated band of smoke has changing characteristics that vary with its local environmental conditions. These conditions may include the physical and chemical nature of the pollutant, weather conditions and downwind topography.
[World Press Review; v41; 24; 1994.] [Journal of Applied Meteorology; v33; 996-1016; 1994.] [Air Quality; Thad Godish; pages 58-64; 1985; Lewis Publishers, Inc; Chelsea, Michigan.]
Source: Atmospheric Chemistry Glossary