Words you use sarcastically when someone is bothering you. They don't really get it but it really means you either want them gone or dead and possibly buring in a hole somewhere outside of town.
Rich: Hey! what's up!? You know, you should really go out with Alyssa
Me: fun stuff *under breath* die!
Rich: what was that?
Me: nothing
a phrase that is usually overused by idiots
"well... FUN STUFF" said Lila Graves. "Bruh can you stop saying that you are such an imbecile" said Maxwell Harries Clarke
Used in turn of the word "Feces" or any other appropriate slang words
Man, that Monkey Fun Stuff smells somthing horrible.