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From Wikipedia:

champignon ‎(plural champignons)

Agaricus bisporus, the mushroom species most commonly used in cooking
2007 January 31, C. J. Chivers, ?A Soviet Agricultural Success: Vast Greenhouse Complex?:

Moscow?s food stores, formerly famed for bare shelves and long lines, are now kept stocked with fresh champignons and greens [?] .

Synonyms

(Agaricus bisporus): button mushroom, cremini, crimini, cultivated mushroom, portobello mushroom, table mushroom