As nouns the difference between mushroom and beefsteak
is that
mushroom is any of the fleshy fruiting bodies]] of [[fungus|fungi typically produced above ground on soil or on their food sources (such as decaying wood) while
beefsteak is a steak cut from beef cattle.
As an adjective mushroom
is having characteristics like those of a mushroom, for example in shape or appearance, speed of growth, or texture.
As a verb mushroom
is to grow quickly to a large size.