A person, (
most of the times black, but not exclusively,) that is annoying, eats chicken and lives off of everybody's back (welfare, begging etc.). A cancer nigger has no manner and no respect for authority and will likely insult or assault you. They show a low level of
intelligence.
The word comes from cancer, the disease, which is often used to describe things or situations that are annoying and from nigger, which is
generally a bad person that everyone hates.