ˈmʌʃˌɹuːm ˈmʌʃˌɹuːm grow and spread fast The problem mushroomed pick or gather mushrooms We went mushrooming in the Fall fleshy body of any of numerous edible fungi a large cloud of rubble and dust shaped like a mushroom and rising into the sky after an explosion (especially of a nuclear bomb) any of various fleshy fungi of the subdivision Basidiomycota consisting of a cap at the end of a stem arising from an underground mycelium mushrooms and related fleshy fungi (including toadstools, puffballs, morels, coral fungi, etc.) common name for an edible agaric (contrasting with the inedible toadstool)