You only have a lemon, by common definition, if it has a persistent defect that substantially impairs its use, value or safety. It's actually rather difficult to end up with a lemon today; production quality across the board is far better today than even five years ago and certainly much more than a generation ago.
But manufacturers certainly mess up on occasion. If your car has had a "reasonable" number of repair attempts for the same defect within the car's warranty period and the defect still hasn't been corrected, the car may qualify as a lemon. If this sounds like your situation, don't fret. With a little persistence, a lot of knowledge and — worst case — the help of a lemon law attorney, you can achieve a satisfactory resolution to your automotive angst: a real fix, another vehicle altogether, or monetary compensation for the piece of junk. Here's how to think about it and what to do.