Dreaming of being angry at someone is a positive dream per meaning and interpretation of dreams. This means realization. You will soon realize that someone whom you trusted was cheating on you. It also means that you will realize your mistakes or you will find out the reason for something bad that happened in your life.
Dreaming of being angry at someone you know means other people might mess up your life. They might damage something you valued dearly.
Dream of being angry at someone you do not know means trouble from strangers.
The dream is also a kind of warning that something bad will soon happen but you need to keep your calm and solve it without getting angry. Anger will only complicate and mess up things.