Dreams of a costume symbolize your desire to be seen in a particular type of role or as a particular archetype. Depending upon the feeling tone of this dream, your subconscious mind is either revealing the type of person you are aspiring to become. See Clothes and Dress.... Strangest Dream Explanations
If you were wearing the costume, you’re hiding your true self from someone - or perhaps from everyone in your circle.
If you take it off, something will cause you to drop the fa?ade very soon.
If you are only one amongst many wearing a costume, especially if some of the others were children, this portends an amazing and totally unexpected - but nonetheless favorable - turn of events.... Dream Explanations of Astro Center
If you dreamed of attending a costume party, where everyone was in costume except you, this is a warning against false friends.
To dream that you are wearing a costume, signifies that you are putting on a false face toward others. Your true self is not being revealed and you are not being completely honest with people around you.... My Dream Interpretation
If you are wearing a costume this could indicate that you are trying to hide your true self, or you inner feelings behind a facade of duplicity; you may not be wholly honest with a loved one and have a fear of being found out.
If you are wearing a ridiculous costume, such as a chicken suit, this could indicate that you are being foolish about certain matters in your life and must look to the other symbols to find out just what it is.... Encyclopedia of Dreams
A facade or charade. Tilings are not as they seem.
Various roles we play in life.
For example, someone who is an authority figure may be seen in a costume depicting a famous leader like Julius Caesar (see Icons).
Mimicry of various real-life scenarios as if in a play. This provides a safe medium for the expression of your perceptions.
Sustenance and support. Among ancient tribal cultures, costumes and masks served as a vehicle for sympathetic magic.
For example, if they needed crops to grow, they might dress as vegetation and perform a jumping dance to encourage that growth. So, what facet of your life does this costume represent, and how does it accent that facet?... The Language of Dreams