1- Being laughed at in dreams suggests we may have a fear of being ridiculed, or may have done something which we feel is not appropriate. We may find ourselves embarrassing. It can also be seen as a sign of rejection.
2- If we ourselves are laughing we may be experiencing a release of tension. Often the object of our amusement will give a clue to the relevance of the dream in everyday life.
To hear a crowd laughing suggests a shared enjoyment.
3- Laughter in the spiritual sense signifies pure joy.... Ten Thousand Dream Dictionary