/ ˈmʌʃrʊm; NAmE ; -ruːm/ noun , verb
a fungus with a round flat head and short stem . Many mushrooms can be eaten :
a field mushroom (= the most common type that is eaten, often just called a 'mushroom', and often grown to be sold)
cream of mushroom soup
—see also button mushroom , toadstool
■ verb [ v ]
to rapidly grow or increase in number :
We expect the market to mushroom in the next two years.
(usually go mushrooming ) to gather mushrooms in a field or wood
late Middle English (originally denoting any fungus having a fleshy fruiting body): from Old French mousseron , from late Latin mussirio(n-) .