According to the Random House Webster's College Dictionary, the term concours d'elegance (from which concours is derived) means "a public exhbiition and competition in which automobiles or other vehicles are judged, chiefly on the basis of elegance and beauty."
Concours is defined as "a public contest or competition."
In the world of vintage Mustangs, it means a highly structured competition among cars that have been restored, as closely as possible, to the exact condition they were in when they left the Ford assembly line. Rules, which are maintained by the Mustang Club of America, are strict and unforgiving of deviations from assembly line conditions---there are even point deductions for making the car look nicer than it was when brand new.
submitted by a65ragtop