When you dream of giants, you have probably ever felt inferior to others, an insignificant person in this world. A fight from your parents to fail an exam, a row from a teacher at school or an incident with your boss at work may have been the cause of this feeling. You feel small in front of the rest, powerless, unable to act.
However, there are other possible interpretations depending on the circumstances of the dream. For example, it doesn't mean the same if a giant chases you (read more about dreaming that they are chasing me) that if you are the large person who tramples a defenseless village. Therefore, it is convenient that you read all the possibilities.