The way I've come to know Zen is that it's just a word and rather than representing a thing Zen is a lack of things; unborn and uncreated. That's why it's elusive. Happiness is the absence of the need for happiness. You could say Zen is the absence of need itself.

You could also call it the absolute Cool!!! if you want to bring it to a bunch of teenagers. If you look at Zen stories they are really about people being insanely cool.