A alternative to the standard door, usually used in high pedestrian traffic areas in an attempt at energy efficiency. Companies selling them claim that they're the most energy efficient entrance system.
Most common are four-wing revolving doors, which provide a large door space with enough room for "wheeled traffic" as well as excellent energy efficiency. Four-wing revolving doors are a popular choice for facilities with a large, continuous traffic flow.
The term is also used as a metaphor for anything that seems to process people quickly and at the expense of compassion and or correctness.