Arvid Svendsen decided that the term muscle car was getting ignored, and used for too many other things, so he made a short list of car descriptions and their definitions that most everyone can agree with

Definition of muscle car:
 Intermediate domestic with big inches (383 and up)—GTO, SS396, 4-4-2, 427 Fairlane, Road Runner, Rebel Machine

Everything else:
Factory hot rod: Fullsize, big motor—Z11 Impala, Pontiac Super Duty Catalina, 1963-1/2 427 Galaxie, 1956 Chrysler 300B with 354 Hemi, 1966 Impala SS427

Junior supercar: Intermediate with high-perf small-block—Olds W-31, 1971 350 Heavy Chevy Chevelle, 1973 Rallye Charger 340

Ponycars: K-code 1965 Mustang, Camaro SS350, Barracuda Formula S 340, Javelin 343

Trans-Am cars: Z/28, Boss 302, AAR ’Cuda

Big-Block ponycars: COPO Camaro, 428 Mach 1, Hemi ’Cuda

Small-block screamer compacts: 1966 Nova L79, 1965 Comet Cyclone K-code 289, Duster 340

Big-inch compacts: 1969 L78 396/375 Nova, 1969 390 SC/Rambler, 1969 M-code 440 Dart

Factory sleeper: 1966 Coronet Hemi four-door

Package race cars: 1968 Hemi Barracuda BO29, 1968 Hemi Dart RO23

Two-seater cool car: AMX

Two-seater kit car (hated): Corvette, Cobra

Arvid Svendsen
https://www.hotrod.com/articles/readers-speak-out-what-makes-a-good-car-show-and-what-exactly-is-a-muscle-car/