U-bolt - Hold the springs to the front and rear car axles.
Underbody - The belly of your car, closest the the ground.
Understeer - When your car turns less than you thought it would.
Upside Down - When you owe more on your vehicle than your vehicle is worth. The value of vehicles depreciates rapidly after the first year of purchase, but a long-lasting loan can cause your cost to be more than the car is valued for.