In the context of the new Facebook react icons, there is one with an angry face. When someone posts a dank meme to offend a group of people, he will type "Boos reacts only" so everyone will react angry instead of liking the meme.
"Boos" is the Dutch word for angry and is pronounced as "boas".

The root of the word reaction. To respond or behave in a particular way in response to something.

A gay person that reacts to stuff. Or a person that acts gay in a weird way.