What is graphic design? and what is a good graphic designer?

A lot of people ask me what I do. When I tell them I'm a graphic designer they stare at me with a blank face, say "huh?" and then ask "but what does that mean?" 

I've tried explaining it to them in words they'll understand but the explanation becomes long-winded and filled with hand gestures and they still don't really know what I mean. 

So, I decided to look it up and create a 15 second "elevator" speech for when I'm asked.

These are some of the definitions I found: