What is "monocopter"

A monocopter or gyropter is a rotorcraft that uses a single rotating blade. The concept is similar to the whirling helicopter seeds that fall from some trees. The name gyropter is sometimes applied to monocopters in which the entire aircraft rotates about its center of mass as it flies. The name "monocopter" has also been applied to the personal jet pack constructed by Andreas Petzoldt.