REEEE is one of the more abstract memes out there, signifying extreme rage and the high-pitched squeal that goes with it. Since it is also mired with the eccentricities of the world of 4chan, it also has undertones of the Pepe the Frog phenomenon and socially maladjusted behavior.
On the base level (and in most of its mainstream usage), REEEE simply refers to a scream. Often it is used as a reaction to someone getting provoked or triggered, like a streamer reacting poorly to a bad beat or an unfortunate turn of events on Twitch. Its usage can range from “pure annoyance” to “intense rage or frustration” depending on the sources, and is therefore more context-dependent than it would perhaps seem based on its simplicity.
In certain ways, REEEE is simply natural. It is meant to emulate the real sound certain frog species make to ward off predators, a phenomenon which garnered great attention on the internet after a popular YouTube video upload and related content on sites like Buzzfeed and Smosh.
Eventually, this scream effect was applied to versions of the Pepe the Frog character with a frustrated expression. Soon thereafter, explanations began to diverge as certain 4chan users also began to reference REEEE as “a typical noise a mentally ill person would make when upset”, adding a negative connotation to the way frustration is expressed via the usage of REEEE. This, however, has not become the exclusive meaning of the meme, not even on 4chan itself, where “Fucking Normies! REEEEEEE!” video and audio content eventually emerged as a general reference of frustration with, well, normies.
Off of 4chan, REEEE is mostly divorced of these connotations and is simply used to signify frustration and rage, either by the person feeling anguish or those watching. On social media sites like Reddit and Imgur, it was combined with the term “repost” to call out duplicate content uploads.
Photo credit: knowyourmeme.com