Wikipedia...NOT the best source for reliable information...but it sure is the quickest.
I didn't read it originally from here, but this is the jist of what I read:
FMR (Front Mid-Engine Rear-Wheel): Where the center of mass of the front-mounted engine is to the rear of the front axle. Like the Vette.
EDIT: I'm not arguing the Corvette is mid-engined, by the way...just to clear that up. The engine is absolutely up front. This is just a technicality I always found kinda neat.