similar to a brown noser
yet the brown thumber can be one or all of the following three things:
1. someone who comes to urbandictionary.com on a regular basis only to thumbs up or thumbs downs the same exact definition in order to boost a friend's or their own definition in a brown nosing
2. someone who not only brown noses others but notices they also enjoy the crude pleasure of objects up the butthole
and does the favor of using their thumb so that person doesn't have to.
3. one who has a brown thumb