n. 1.common name for an edible agaric (contrasting with the inedible toadstool) 2.any of various fleshy fungi of the subdivision Basidiomycota consisting of a cap at the end of a stem arising from an underground mycelium 3.a large cloud of rubble and dust shaped like a mushroom and rising into the sky after an explosion (especially of a nuclear bomb) 4.fleshy body of any of numerous edible fungi mushroom v. 1.pick or gather mushrooms 2.grow and spread fast