I was driving in a car at the time of observation; observation was degraded by automobile lights, nearby highway illumination signs, windshield reflections. At first I thought it was a close, fast-moving helicopter, but continued observation left me questioning that. I *thought* I saw some slight sputtering/tail debris, but cannot be positive. It seemed to be moving far too quickly to be an aircraft given the apparent distance it would have had to travelled and me not be able to make out anything other than the white light I saw. I specifically looked for blinking red aircraft lights and saw none. I was able to watch it as it faded and dimmed completely and it appeared more like a dimming fireball instead of an aircraft light pointing away (adding evidence that it was not an aircraft), however given the poor observing conditions I cannot assure that it was not an aircraft. Adding to the unusual nature was that it *appeared* to be moving directly E-W at constant altitude. The trajectory looked like that of an aircraft, but the speed and other factors make it unlike any other nighttime aircraft observation I have ever seen. From my evidence, I am judging probability 50% fireball, 50% misidentified aircraft/other.