1. Like a toothbrush for your ass hole; it scrubs the crustified dung off of one's ass hairs while providing a sandpaper-esque feeling on the soft tissue of your rectum
2. Any bristled object used to clean a dirty homeless invalid, against his or her will, while they lay half-dead beside a trash heep asking for spare change
3. A sand paper covered dildo for use by any man or woman who either likes the feeling of blood running out of his or her butt, has lost all feeling in the anal cavity due to excess butt-dildo-use and therefore needs the bumscrubber for any sort of titilating stimulation, or really just likes a very clean and irritated inner anus
I went to the radiologist the other day for an x-ray and they found that bumscrubber I lost a couple weeks ago.
"Come here you dirty bum and get your scrubbin," said the angry bum hater. "Oh no, not the bumscrubber, it hurts so bad!" said the dirty bum.