Especially if I'm trying to get something done, I just say it is a computer, and leave it at that. I really couldn't care less if people know what it really is, or not. At first I wanted to show it off to everyone, but now, meh.
If the person I'm talking to is really into computers and will understand it's true potential I'll tell them. Otherwise I don't waste my breath...

Sort of like my laptop, I do pretty much everything on the command line, which confuses most people, but I have given up explaining it. Same with the dvorak keyboard layout..
So I guess I answered my own question