Whatever the answer is, I know it's a complicated one. I've just thumbed through my Concise Oxford English Dictionary for a spot of help and come up with the thoroughly woolly description of a supercar as "a high-performance sports car".
What I can tell you, however, is that the C6 Corvette ZR-1 is most definitely and most assuredly a full-on supercar. Supercar status is not something that has been bestowed on the Corvette before now, but it was surely only a matter of time (and, possibly, horsepower).
Think about it. The muscle car tendencies of the Corvette already endow it with certain supercar attributes. There's that sharp-looking body, not inconsiderable girth and a variety of large-capacity V8s. Oh, and it's also got the added impracticality of left-hand drive. Very supercar.
What complicates matters with the 'Vette is that it apparently fails a few crucial supercar tests. The engine, being in front of the driver, is in the wrong place for starters. Now, this isn't a red-card offence for a supercar, but there are only a handful of models out there that could even apply for entry to such an exclusive club. The ZR-1 can try to ape its mid-engined rivals all it likes with the Perspex window onto the engine cover but, rather than looking mid-engined, it just looks a little crass. It's also cheap by supercar standards. £106k? Hah, pittance (look at the price of a Veyron or an F40). Finally, it's not German, British or Italian, which puts the Yank on rather a back foot in such elitist, old-money company.
Wilton House Supercar Show near Salisbury. Could the ZR-1 stand comparison with F40s, Veyrons, McLaren F1s, Diablos and Enzos?
The Corvette scores a partial victory immediately as we wait to set off. Despite some seriously exalted company the Corvette is holding its own and drawing plenty of attention. Even if that's only because of its sheer rarity, that has to be chalked up as a bit of a victory.
As we head out of London and onto more open roads the task facing the Corvette is apparent; every time the M3 crests a brow there before it is a line - as far as the eye can see - of gobsmackingly exotic metal. The 'Vette is not cowed, though (if you'll excuse the unintended pun); that 638bhp V8 lump means the humble Corvette can stay with anything this side of a Veyron.
Before we reach Wilton House we make a detour via Gurston Down hill climb course. It represents a great opportunity to put the ZR-1 through its dynamic paces in something other than a straight line. This is the only hill climb course in the country that starts downhill and, being a hill climb course, it's narrow and tight, and a seriously tough test for a car as big, wide and powerful as the ZR-1.
I tackle the hill carefully, but for such a big car the ZR-1 copes with the narrow confines of Gurston with aplomb. You can't let its copious amounts of power of the reins much, but the brakes are strong and there's grip to spare. It's even surprisingly agile around Gurston's tight hairpins. Switching the traction control off is a game only for the strong-stomached, however; with all that power and so little weight over the rear wheels, a smoky exit from slow corners is but an accidental twitch of the right foot away.
So has the ZR-1 proved its supercar mettle? It's certainly as fast, capable and exotic as the most super of supercars, but speed and power are just some of the numbers in supercar maths. Corvette ZR-1 = supercar? We'll leave you to balance that particular equation.
2009 Corvette ZR1 Coupe
Type Aluminium frame with composite and carbon-fibre body panels
Body Style Coupe hatchback (2-door)
6.2-litre supercharged V8 (647 ps)
Eight-cylinder in 90-degree V, 16 valves
Max power 647 ps (476 kW) @ 6500 rpm
Max torque 604 lb ft (819 Nm) @ 3800 rpm
Fuel system Electronic multi-point injection
Drivetrain & Transmission
Rear-wheel drive, limited-slip differential, electronic traction control
6-speed manual transmission
Suspension & Damping
Front Fully independent by double wishbones, with transverse composite leaf-spring and Magnetic Selective Ride Control damping system. Anti-roll bar.
Rear Fully independent by double wishbones, with transverse composite leaf-springs and Magnetic Selective Ride Control damping system. Anti-roll bar.
Type Hydraulic speed-sensitive power-assisted rack and pinion
Lock-to-lock 2.78 turns
Turning Circle 12.0 metres
Front 394 mm diameter carbon ceramic ventilated discs, six-piston calipers
Rear 380 mm diameter carbon ceramic ventilated discs, four-piston calipers
ABS 4-channel anti-lock system with EBD, MBA and CBC
Wheels & Tyres
Front Alloy 19 x 10J inch with 285/30 ZR19 run-flat tyres
Rear Alloy 20 x 12.0J inch with 325/25 ZR20 run-flat tyres
Overall length 4459
Overall width 1927 (excluding door mirrors)
Overall height 1246
Front track 1607
Rear track 1580
Fuel tank 69 litres
Kerb weight (kg) 1528
Maximum (kg) 1755
Weight distribution 51/49 (% front/rear)
0-to-62 mph (sec) 3.6
Top speed (mph) 205
Fuel Consumption and C02 rating
Combined (mpg) 18.8
C02 (g/km) 355