What does it mean to dream of a tiger?

Since dreams are usually a harmless subconscious manifestation at night of your own human thoughts and actions during the day, and that everybody's thoughts and thought-processes are unique, it follows that tigers (or whatever) can usually mean anything. If you are using mind-altering drugs, pot, alcohol, or are on medication, these will also affect dreams, but you are in control of the gateway to your mind.

During the night your mind is still sub-consciously working on what you were consciously doing during the day, so if you had been watching "Jungle Book" and saw Mogile fleeing from the evil tiger "Sher-Knan" a tiger would mean "RUN, FLEE FOR YOUR LIFE".