1. An insulting term for a despicable or objectionable person: The arrogant dictator considered the protesters to be scumbags for protesting the unfair policies of the government.
2. Someone who is considered to be sleazy, dirty, or disreputable; such as, a totally disgusting person who is considered to be rude and derogatory: The youth leader used to be considered a scumbag, but after working in the local youth shelter, he has turned his life around.

The park officials urged the clean-up crew to use rubber gloves when picking up scumbags left under the trees after the riotous rock concert.