Noun
(folklore, Cornwall, Devon, Gloucestershire, Somerset) Grass growing in a circle that possesses the magical power of compelling anyone standing within it to confess their wrongdoings.
(folklore, Cornwall, Devon, Gloucestershire, Somerset) A magical circle of grass believed to have been created by pixies, that causes any mortal stepping into it to believe they are continuing to walk forward when they are actually walking in a circle.
Source: en.wiktionary.org