It really is as quick as typing "wicca" on Google.

That said, if you want the "Reader's Digest" version of what Wicca (btw, "wiccanism" is not even remotely a real word) is, here is what I would tell someone in an elevator, as you said, if they asked:

***Wicca is a reconstructionist neopagan religion based on old folk religious practices, that incorporates a reverence for and celebration of nature and its cycles, a belief that subtle forces exist and can influence the physical world, the idea that we are more than just our physical bodies, and the belief that our actions, good or bad, will bring natural consequences in this life or another.***

Now, kat mentioned that they didn't see where Wicca fit in with other religions, and one of the reasons for religion being an "opiate" for opressed masses. And I agree! Wicca is not like other religions in that regard, as it promotes personal empowerment and thinking for oneself. So while some religions tell people how to go about just about every aspect of their lives, Wicca teaches one to follow their own path and work out their own will.