F'jack: v; used to describe when someone is doing something.
F'jackn is the art of F'jackinating.
This word was first used in a Math class in The Science Academy, since then it has been widely spread.
You:Dude are you F'jackn?
Friend:Why yes I am.
You:Are you f***ing with me?
Friend:Naw, I'm just F'jackn with you.