What is "cool"?

So I have thought in the past some about what "cool" is. At the time the best I could come up with was examples. Like Arthur Fonzarelli from Happy Days:

I was recently reading an interview in Make Magazine with Adam Savage, one of the ever-popular Mythbusters. The interviewer, Paul Spinrad, points out that enthusiasm is the opposite of cool. My first response was "huh?!?" But further explanation and discussion with Adam points out some interesting things. First, it's children that are most often overly enthusiastic. There becomes a point, however, when a more grown up child finds that enthusiasm immature (or perhaps "dorky") and invents (or steals, at this point) "cool" as an alternative. Not caring about what someone else cares about is a way to sort of "take it away."

That's an interesting way to think about it, and kind of useful to me as a parent. Much like anything out there, it's fine to be a little "cool", but it's also easy to go overboard with it. Thinking about it in these terms will help me help my kids better understand why it's bad to act some ways. This could be particularly important for folks with multiple kids with ages that vary widely.

I don't know, just something to think about.