The practice of changing the zoning in an area typically from residential to increased commerical use. This is a controversial practice because upzoning allows for greater density and conjestion in the area which affects the current occupants. The term can also apply when changing the zoning to limit growth and density.
The process, often controversial, of changing the zoning in an area, usually to allow greater density or commercial use. Sometimes the term is used to mean the opposite -- changing the zoning in a broad area to limit growth and density.