Jokes, phrases and the like that only the people in your office will understand. Folks outside of your department or organization will laugh but they won't understand the joke because they in essence "had to be there"
Worker: "I just removed myself from that post on Facebook"
Co-Worker: "You mean you "Miked" it?" -wink, wink, nudge nudge
Other Co-Worker: "You did what?"
Worker: Never mind it's just an inter-office meme, you wouldn't understand