Read the dictionary definition of scummy. All definitions for this word.
1. covered with scum
1. the scummy surface of the polluted pond
2. of the most contemptible kind
1. abject cowardice
2. a low stunt to pull
3. a low-down sneak
4. his miserable treatment of his family
5. You miserable skunk!
6. a scummy rabble
7. a scurvy trick