a ring of dark luxuriant vegetation in grassy ground corresponding to the edge of an underground fungal mycelium: popularly associated with the dancing of fairies: seasonally marked by a ring of mushrooms
2.
short for fairy ring mushroom, Marasmius oreades, a dainty buff-coloured edible basidiomycetous fungus, characteristically forming rings in grassland
fairy ring in American English
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