The Definition of "MuscleCar"

The first true muscle car was the Pontiac Tempest with the GTO package. 389 with tri power. The idea was to start putting the big motors of the full size cars into intermediate body styles. Do not confuse them with Pony cars from the same era as these were the compact(buy 1960's standards) body styles.
Muscle cars:
Roadrunner
Super Bee
442
Chevelle
Torino
Cyclone
Cougar
GTO
GS/GSX

Pony cars:
Barracuda
Challanger
Cuda
Camaro
Nova
Firebird
Mustang
Dart
AMX


This is a generic and short list but it gives an idea of what constitutes a "Muscle Car".
On the pony car list, naturally not every model line up makes the list but that was the body style the hot rods were based on.
The e-bodies were the biggest of the Pony cars and could go either way.

Funny story, some years back I was at a training meeting for work, we had to fill out index card with some hobbies/interest. Well I put "working on muscle cars". We had to give our card to the person next to us and they read it. Nobody new what a muscle car was and I tried to explain a little and someone yells out "like a mustang", then the class instructor says "more like a Roadrunner".:-D It was priceless. 8)

This is just my opinion and not based on any facts other then what I have read in books over the years. Please feel free to comment on anything here.