If you dream that you manslaughter someone, then it means you are having anger issues on this particular person and therefore you are dreaming about it. If you are the one who manslaughters someone in order to defend yourself, then it means you are the person who has some issues with another one. The dream shows that you are jealous about something or have the anger towards that particular person. If you dream that you do some damage for that certain person, you will achieve success. Alternatively, the dream means that you are very selfish therefore you are being manslaughter.
Read more about dreaming of Manslaughter in other dream meanings interpretations.