Definition of "mushroom" []

• Any of various fleshy fungi of the class Basidiomycota, characteristically having an umbrella-shaped cap borne on a stalk, especially any of the edible kinds, as those of the genus Agaricus. (noun)
• Something shaped like one of these fungi. (noun)
• To multiply, grow, or expand rapidly: The population mushroomed in the postwar decades. (verb-intransitive)
• To swell or spread out into a shape similar to a mushroom. (verb-intransitive)
• Relating to, consisting of, or containing mushrooms: mushroom sauce. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "Each tin mushroom is numbered and represents one mushroom left in reality."
• "Some apply the term mushroom to a single species, the one in cultivation, and which grows also in fields (_Agaricus campestris_), and call all others toadstools."
• "It is becoming customary with some students to apply the term mushroom to the entire group of higher fungi to which the mushroom belongs (_Basidiomycetes_), and toadstool is regarded as a synonymous term, since there is, strictly speaking, no distinction between a mushroom and a toadstool."