The head in dream is a very important symbol, which represents the qualities of the dreamer such as intelligence, wisdom, mind rational thinking. The dream could also signify the view dreamer has about his own image. If someone is trying to rip your head off, then such dream symbolizes some situation in your waking life which you are not able to acknowledge. There is possibility that you are trying to avoid in seeing the reality. The dream suggests you to start looking at things the way they are, instead of fantasizing that everything is fine and there is no need to do something.
Read more about dreaming of Head in other dream meanings interpretations.