a Phys-Ed course. My work schedule interfered and I just dropped it after the timeframe for withdrawals. I retook the class later and was surprised to see that it didn't come off my record as an "F" equivalent! At that college PE courses could be taken as you wanted, so they did not replace the previous grade, they just added another credit.
I didn't get any Ws or UWs at BYU, and didn't take any PE courses, so I just mention this as an unusual possible issue with UWs.