Muscle car definitions?

I'm confused. I was looking at the Muscle Car Club definition of muscle cars page where it lists what cars are muscle & what cars are not. When I got down to the Barracuda section I got confused. Is there a difference between a Barracuda and a 'cuda? Then it says that Barracudas with a 340 are not considered muscle cars but Dusters with 340s are. Here's the link:

http://www.musclecarclub.com/musclecars/general/musclecars-definition.shtml

My '65 Barracuda has the 273 Commando with a 4bbl. I assume that this little car is NOT a muscle car so I enter it in the Mopar or Original Car or A Body categories at the shows. I'm pretty clear on most of the muscle cars but I get a little fuzzy on the pony cars.