1: a ring of basidiomycetous mushrooms produced at the periphery of a body of mycelium which has grown outward from an initial growth point also: a ring of luxuriant vegetation especially when associated with these mushrooms
2: a mushroom (especially Marasmius oreades) that commonly grows in fairy rings
First Known Use of fairy ring
1870, in the meaning defined at sense 1
History and Etymology for fairy ring
from the folk belief that such rings were dancing places of the fairies