Scummy (adjective)

1. Covered in or consisting of scum.
2. Morally or ethically contemptible; disreputable.

Origin:

Origin unknown.

Examples:

1. The pond was scummy and smelled terrible.
2. He had a scummy reputation and was not well liked.
3. The water was so scummy that it was not safe to swim.
4. The scummy film on the surface of the water was caused by pollution.
5. He was considered a scummy person and no one wanted to associate with him.