Any very fast, lightweight, high mpg vehicle which resembles a cross between a motorcycle and a car. It has a car-like front end, ie, two steering wheels in front, a windshield, and two car seats, often taken from an actual car. And a motorcycle rearend. A motorcycle engine, placed amidship, and a single motorcycle wheel&tire in the back. They are rear-wheel-drive.
Trikecars handle MUCH better than the old ATV 3 wheelers or motortrikes with a Motorcycle front and a car-like rear end.
A perfect example of a trikecar is the T-rex (or the extinct Tri-Hawk).
The only trikes with 1 wheel in front, and 2 in back that handle really well are those that LEAN. The CARVER is a perfect example. Much like GM's old Lean Machine show vehicle.