A defective vehicle, commonly referred to as a 'LEMON, ' is a vehicle that has been found to have a significant defect or malfunction that cannot be repaired. This term is often used to describe cars, trucks, and other motor vehicles that have been deemed unsafe or unreliable due to their defects. The term is derived from the fact that lemons are known for being sour and unpleasant, which is how many people feel about a defective vehicle.