I. mush ‧ room 1 S3 /ˈmʌʃruːm, -rʊm/ BrE AmE noun [countable]
[ Date: 1400-1500 ; Language: French ; Origin: mousseron , from Latin mussirio ]
one of several kinds of ↑ fungus with stems and round tops, some of which can be eaten ⇨ toadstool :
mushroom soup
⇨ ↑ magic mushroom
II. mushroom 2 BrE AmE verb [intransitive]
to grow and develop very quickly:
New housing developments mushroomed on the edge of town.