Agaricus campestris

Mushroom Mush"room, n. [OE. muscheron, OF. mouscheron, F. mousseron; perhaps fr. mousse moss, of German origin. See {Moss}.] 1. (Bot.) (a) An edible fungus ({Agaricus campestris}), having a white stalk which bears a convex or oven flattish expanded portion called the pileus. This is whitish and silky or somewhat scaly above, and bears on the under side radiating gills which are at first flesh-colored, but gradually become brown. The plant grows in rich pastures and is proverbial for rapidity of growth and shortness of duration. It has a pleasant smell, and is largely used as food. It is also cultivated from spawn. (b) Any large fungus developing a visible fruiting body with a stem and cap, usu. of the basidiomycetes; especially one of the genus {Agaricus}; a toadstool. Several species are edible; but many are very poisonous. The term mushroom is used most often for edible varieties, the poisonous ones being termed {toadstools} or other names. But this distinction is often ignored. [1913 Webster +PJC]

2. One who rises suddenly from a low condition in life; an upstart. --Bacon. [1913 Webster]