To increase in number suddenly and rapidly (as mushrooms often do). Even though I'm constantly tending to my garden, the weeds just spring up like mushrooms nonetheless.I thought I only had a transmission problem, but other issues with the car are now springing up like mushrooms.
Fig. to grow suddenly into something large or important. The question of pay suddenly mushroomed into a major matter.The unpaid bill mushroomed into a nasty argument and, finally, a court battle.
n. mushrooms of the genus Psilocybe, which cause visions or hallucinations when eaten. (Drugs.) Magic mushrooms are okay because they are natural, or something like that. They sometimes call peyote cactus buds, the “sacred mushrooms.”