the media is just an easier way of saying, bioballs, chips, rings, filter pads, sponges, or cartridges. It is the part of your filter that harbors the bacterial colony.
Super G. a fast rinse with tap water works okay as long as the chlorine level of the water is not to high, some bacteria are killed but some survive. if too many die you will get a temporary increase in ammonia levels.
You could theoretically fill a bucket w/ tap water, let it "age" over a few days, and pop in some dechlorinator. Then, it's basically clean water w/o having to be cleaned in the old tankwater.