mushroom

1 of 2

noun

mush·​room ˈməsh-ˌrüm 

-ˌru̇m;

chiefly Northern and Midland US -ˌrün;

dialectal ˈmə-shə-ˌrüm, 

-ˌru̇m, 

-ˌrün

1

a

: an enlarged complex aboveground fleshy fruiting body of a fungus (such as a basidiomycete) that consists typically of a stem bearing a pileus

especially : one that is edible

b

: fungus

2

: upstart

3

: something resembling a mushroom

mushroom

2 of 2

verb

mushroomed; mushrooming; mushrooms

intransitive verb

1

a

: to well up and spread out laterally from a central source

b

: to become enlarged or extended : grow

2

: to collect wild mushrooms

3

: to spring up suddenly or multiply rapidly

Synonyms of mushroom

Verb

• increase
• rise
• swell
• accelerate
• wax
• expand
• climb

Examples of mushroom in a Sentence

Noun

cut up some mushrooms for the salad

Verb

Interest in local history is suddenly mushrooming.

Her hobby mushroomed into a thriving business.

He goes mushrooming in the spring every year.

Recent Examples on the Web

Noun

Shop Vogue’s favorite mushroom chocolate, below. —Brianna Peters, Vogue, 28 Mar. 2026

Oregon became the first state to legalize psilocybin mushrooms in 2020, rolling out regulated psilocybin services in 2023. —Natalia V. Osipova, CNN Money, 28 Mar. 2026

Verb

After these bonds and all the other debt piled onto the city’s books by Johnson and previous mayors, the city’s annual debt service for general-obligation (GO) bonds is set to mushroom to $627 million in 2029 from $366 million next year, a 71% increase, according to the bond document. —The Editorial Board, Chicago Tribune, 22 Mar. 2026

But great replacement theorists wildly exaggerate demographic changes involving migrants of color in order to present them as a mushrooming threat to White people. —Literary Hub, 18 Mar. 2026

Word History

Etymology

Noun

Middle English musheron, from Anglo-French musherum, musseron, from Late Latin mussirion-, mussirio

First Known Use

Noun

15th century, in the meaning defined at sense 1a

Verb

1893, in the meaning defined at sense 1a

Phrases Containing mushroom

• button mushroom
• Chaga mushroom
• chicken mushroom
• enokidake mushroom
• enoki mushroom
• enokitake mushroom
• field mushroom
• lion's mane mushroom
• magic mushroom
• meadow mushroom
• mushroom cap
• mushroom cloud
• oyster mushroom
• sacred mushroom
• straw mushroom
• sulfur mushroom

Kids Definition

mushroom

1 of 2 noun

mush·​room ˈməsh-ˌrüm 

-ˌru̇m

1

: a fleshy part of a fungus that bears spores, grows above ground, and consists usually of a stem bearing a flattened cap

especially : one that is edible

2

: fungus sense 1

mushroom

2 of 2 verb

: to appear or develop suddenly or increase rapidly

the population mushroomed

Medical Definition

mushroom

noun

mush·​room ˈməsh-ˌrüm  -ˌru̇m 

1

: an enlarged complex fleshy fruiting body of a fungus (as most basidiomycetes) that arises from an underground mycelium and consists typically of a stem bearing a spore-bearing structure

especially : one that is edible compare toadstool

2

: fungus sense 1