A fact is a something proven to be true. A fat fact is when someone says something you can relate to and is just an obviously true. Since it’s so relatable it makes it a FAT FACT. It may also be pronounced as Fat Fax
Billy: Spring Break is going to be Lit!
John: FAT FACTS!
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"