some of my most dance-like conversations happened when there was no common vocabulary at all, but somehow this made us able to understand each other a lot better than we would have if we did know 300 of the same words (i've tried that too)
other than that, i have a friend with whom i can speak about anything without any concern for how the words come out, she does the same with me, and we very often have read the other's mind before the words are spoken. or we might say the same thing at the same time. it's fun, but we often end up talking about things that might scare people who don't understand how our minds work