It means the game state is corrupted. Players are no longer observing a consistent state. Things could be happening on your screen that isn't happening on another player's. You might as well restart the game when you see this because the desync message is annoying as hell and because there's little point in continuing to play with a corrupted game state.

I've gotten this several times in Pantheon matches.  I could talk to the people on the other team who it said were desynced, but we were playing two different games.  From my side my team won, and they won from their point of view.  Strange considering we could still communicate.

It does not.

Your sentances look worse then your profile and you will never amount to anything as a flamer.

WTF? I'm not 19