At the BlogHer conference last month, we were given the opportunity to do a "speed dating" exercise where we met about a dozen attendees in the space of 15 minutes. It was a fun way to meet a cross-section of the 750 attendees.
It also gave me impetus to review how I talk about what I do with KM. Here's essentially what I came up with:
How are people using technology, information and one another to get work done (or solve problems).
I like this because it clarifies that KM is a combination of the elements that I think are important in KM: people, technology and information. One might want to add "environment" in there, but I wasn't quite sure how to make it work succinctly.
The other aspect of this definition is that it is rather generic. If you are working at a strategic level, you get to think about how you want these things to happen. If you are working tactically, you get to think about what you are doing with what you have.
Note: I have to give partial credit to the Center for Learning and Organizational Change at Northwestern, where I am an adjunct professor. This definition has definitely been inspired by my interaction with the people there.