Personally I like to use the word fixie because it ruffles a lot of feathers among those who take themselves too seriously. I freely refer to my Wabi as a fixie and my Dolan as a track bike. To me FG bikes on the road are fixies and FG bikes on the track are track bikes.

So for me it's about the application and less the machine. But that's just the way I like to use those terms.