After you've hung out around a friend (especially a geek friend) or SO for far too long, you may notice that you have your own secret language. Not the kind that twins have as children, but a language composed entirely of in-jokes that have grown out of gaming sessions, favorite movies, and embarrassing events. Using Injokese in public tends to get you strange looks, and using it when two different sets of friends are together can cause failure to communicate. Eventually, you'll find that you forget the origin of the phrases, but retain their new mutated meaning. At this point you should consider finding new friends. (Not really. Friends are too valuable to lose just because you sound like idiots whenever you have a conversation.)

This is all well and good, but it can be used for a less-silly purpose. When 7Ghent brought a girl along on one of our day hikes in the Sandia Mountains, and the group collectively perceived her as being "not like us", we put our impenetrable walls up and no interesting communication was possible. This wasn't entirely our fault; when one of us tentatively tried to talk with her, she was, shall we say, less than forthcoming.

The intimacy that is implied by the use of such language can be very offputting to some people. So watch out.