fairy ring definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a circle of mushrooms often seen on grassy ground, originating from one initial mycelium and often accompanied by a circle of darker grass: so called because formerly thought to have been made by the dancing of fairies
fairy ring definition by American Heritage Dictionary
A circle of mushrooms in a grassy area, marking the periphery of perennial underground mycelial growth.
Origin: From the belief that it is a dancing place for fairies.