If you dream of barbarian, it symbolizes the wild side of your personality. This dream indicates how much of the wildness is in you, it shows how fierce and barbarous you are.
Dream dictionary: Barbarian dream meanings
To act as one committing a barbarous action, means that you will suffer sorrow and sincere repentance.
If you had a dream about the cavemen, then such dream symbolizes the basic instincts of human. To get more interpretation of your dream, please chech the meaning of Barbarian.