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