An extremely pithy description of something, prepared in advance to be used in situations where time is of the essence. The term comes from the hyopthetical situation of somebody seeing a pin or something similar on your person that arouses their curiosity while in an elevator (such as a Unitarian Universalist chalice pin), and then asking you what exactly the pin stands for. Because Unitarian Universalism would be rather difficult to explain in the remaining duration of the elevator ride, the prepared elevator speech serves to provide as best of an answer as possible in the available time.
So, how do you explain Unitarian Universalism to people without putting them to sleep?
Well, my standard elevator speech emphasizes secular humanism and free thought.