The Definition of "MuscleCar"

Okay guys I made this thread because I noticed some discussion in another thread regarding the definition of what is muscle and what isn't. So please define what constitutes muscle in your opinion. The way I see it my 74 Dodge Dart with a mild 318 isn't necessarily hard core muscle, but it's been modded a bit and isn't exactly an economy machine either. So how much horsepower does a motor have to put out before truly becoming "muscle"? 300HP? 400HP? 500HP? A trailer queen that is so modded that it cannot be driven on the street? Or is muscle any cool looking American iron that has been modded a bit, goes pretty quick, and sounds cool?