Cham·pi'gnon noun [ French, a mushroom, ultimately from Latin campus field. See Camp .] (Botany) An edible species of mushroom ( Agaricus campestris ). Fairy ring champignon , the Marasmius oreades , which has a strong flavor but is edible. Found on http://www.encyclo.co.uk/webster/C/53
Champignon is a name given to the common mushroom of Britain (Agaricus campestris) and also to the edible fairy-ring fungus Marasmius oreades. Found on http://www.probertencyclopaedia.com/browse/BC.HTM
Any of a number of edible fungi (see fungus). The fairy ring champignon (Marasmius oreades) has this name because its fruiting bodies (mushrooms) grow in rings around the outer edge of the underground mycelium (threadlike body) of the fungus. (Family Agaricaceae.) Found on https://www.encyclo.co.uk/local/21221