Shitty degenerates who mostly strive to attack people, usually a big group of shitty friends but they're now expanding their awful, awful pack.
They originate from G+, and aren't as special anymore.
Jesse: Aren't you glad that James of the shroomboy's got suspended? If only it was permanent..
Hannah: Yeah, he's pretty gay, dude. He doesn't deserve the respect he gets.
An insult that is synonymous with soyboy, virgin, incel, nolifer, basement dweller, etc
To be referred to as a "shroomboy" is to be implied as one or all of these synonyms. It also implies that the jizz sock you use has literal mushrooms growing on it, and perhaps even on yourself, because of how much of a disgustingindividual you are.
Riley: Bruh, what's a shroomboy?
Huey: Scummy, fungus ass mufuckas that even 4chan anon niggas don't fuck with.