When you tell a joke to someone while dreaming, then such dream symbolizes the negative attitude you receive from other people. People do not take seriously in what you are saying, therefore you are telling jokes in this dream. Alternatively, the dream could symbolize how funny and lovable you are by others. If you heard a joke that was told by somebody else in a dream, then it foretells about some situation which is pointless and you shouldnt put effort while dealing with it. The joke that was told by someone else could also indicate some stress that is released by now.
Read more about dreaming of Joke in other dream meanings interpretations.