A more psychological definition of ambient abuse is "an increasing frequency of systematically withholding factual information from, and/or providing false information to, the victim - having the gradual effect of making them anxious, confused, and less able to trust their own memory and perception.
Or maybe your boss gets angry because you didn't prepare the report he asked you to. When you remind him that he usually prepares that particular report, he snaps that he told you to take care of it a few days ago because he was too busy. However, you know he never asked you to do so.
Both of these could be considered ambient abuse.