What does it mean when you dream of running from someone?

It depends whom you are running from. If it is a stranger, it could be a warning to stay away from them.

More information:

Dreams of running away from something are often figurative representations of the dreamer running away from some problem in real life. For example, one might want to "run away" from unpaid bills, an upcoming exam or a confrontation with a certain person. When one tries to avoid unpleasant issues, the subconscious mind will present a dream of literally running away. Sometimes such dreams can be resolved through lucid dreaming, in which the dreamer stops running, turns around and discovers what it is they are running from, all during the process of dreaming. Perhaps a better solution would be to figure out what one is avoiding in real life and deal directly with that issue. Then the running dreams will stop.