1. noun, slang An informal shortening of "mushroom." Used primarily in plural constructions; sometimes spelled with an apostrophe to indicate the abbreviation. No shrooms on my pizza, please! I'm going 'shroom picking with my uncle in the woods behind our house—want to come?

2. noun, slang A mushroom containing psilocybin, a compound with psychoactive effects when ingested. Used almost exclusively in plural constructions. I ate way too many shrooms and had the trippiest night of my life! I only do weed and shrooms because they grow naturally in the ground—I stay away from powders and pills.

3. verb, slang To ingest psilocybin mushrooms in order to experience their mind-altering effects. I used to shroom all the time when I was in college, but these days, it seems to really mess with my mental health. There were a bunch of people shrooming at the concert.