This comic starts with a quote from from the Lewis Carroll book Through the Looking Glass. If a speaker (Humpty Dumpty, in this case) ascribes his own meaning to words, he can always change what he meant to say after the fact, and so gives himself an way out of whatever he said earlier. However, if you're not using word definitions that are normally agreed upon and that the listener knows, you may as well be spouting nonsense. Humpty Dumpty wouldn't be the only Carroll character doing that, although Carroll at least insisted that the nonsense be internally consistent. The problem for the speaker is that people will eventually stop listening to nonsense. Randall Munroe took the power of defining words away from the speaker and gave it to the listener, resulting in some karma for messing around with our common language. This is the latest comic from XKCD.