One who kisses ass or brown-noses constantly. A person who can not get by on his/her own merit. One who MUST "suck up" or "kiss ass" to get by. This type of person VERY often will also step on others around them or snitch and squeal on others to make themself look better and to advance themself, due to his/her own lack of ability/qualification/education. A "ButtMunch" will often break his/her own arm while patting themself on the back.
This person is a brown-noser to an extreme degree.