What's the actual definition of muscle car?

A time-honored standard for insurance purposes is 10.5 lbs or less per horsepower.

The original Muscle Cars were never sedans; two doors only. All were mid-size car models with large displacement engines, with either standard or automatic transmission. These days, anything fast is considered a muscle car, but rarely do they fit the original "definition." A Jeep Cherokee (SUV) would never be considered a muscle car. Taurus SHO is a high-performance sedan. The BMW M5 would be a European high-performance car, sedan or coupe. And L'invincible, Mustangs were Pony Cars, not muscle cars back when the factories actually made muscle cars.

Typically: American Made (though Australians were pretty good at them too, plus Canadians usually contributed to the design and manufacture). Family car based. 2+2 seating. Rear wheel drive. V8 (though turbo and supercharged V6s and even turbo 4s have been offered as higher performance models than V8s, and today's V6s perform better than V8s from 20 years ago). Emphasis on off the line straight acceleration, with significant sacrifices in top speed, handling, and braking in comparison to similarly powered cars. The M5 is not a muscle car. It will blow away just about any true muscle car at a track with two full sized adults in the back and a trunk full of golf clubs. The new Camaro is not really a muscle car either, With its fully independent suspension, it posts enviable Nürburgring times.

the only auto maker even toying with a muscle car is gm. the new model camaro with the radio delete, etc. muscle cars were midsized auto's with huge engines and stripped to the bare essentials.. no radio, usually no ac, no ps, no spare tire, etc the muscle car died long ago, youve listed performance cars. muscle cars were for 1 thing, race purposes, and generally 1/4 mile.