Ree

Ree is the mating call of the autismo. It's a high-pitched noise that sounds something like this: REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!111!1! There are many variants of the ree concerning the pitch and length, but they're all pretty much the same.

Origins
Ree started out as a sound made by Pepe the Frog, but then some autismo somewhere picked it up, used it in school, and that became the national anthem of retards everywhere.

Figurative ree
When someone is figuratively reeing, they're complaining about some shit no one cares about like how an autismo would.