Crop circles are patterns created by the flattening of crops such as wheat, barley, rye, or corn.
The term crop circle was first used by paranormal researcher Colin Andrew to describe simple circles he was researching. While patterns involving complex geometries have been observed, the term circle has stuck as a generic term for crop patterns.
Bower and Chorley claimed to have started the crop circle phenomenon in 1978 and were awarded an Ig Nobel Prize in 1992 for their crop circle hoaxing.
There is no evidence that crop circles are anything but man-made hoaxes or works of art. Nevertheless various alternative hypotheses have been offered to explain the formation of crop circles such as the paranormal. It has also been suggested that ball lightning and vortices in the wind might rarely produce isolated indentations in crops. [wiki]