Halloween Costume
To dream of a Halloween costume represents feelings about you or someone else that changes themselves to scare other people. It may also reflect feelings about how you or someone else chooses to scare someone else into changing. A false negative persona. You may be trying to appear angrier or more dangerous than you really are. It may also reflect a deceptive attempt to scare other people. You or someone else that feels good pretending to have a negative or dangerous attitude. Not really being serious about how negative or dangerous you are acting. A phony negative persona.
Alternatively, dreaming about a Halloween costume may reflect enjoying yourself faking being something you are not or enjoying a rare opportunity to pretend to be something you are not. A situation so ridiculous you need to perfectly believe you are something you're not.
To dream of a Halloween mask represents feelings about faking your personality to scare someone into changing themselves for you. Feeling good noticing you are behaving in a way to scare someone into giving you something. Feeling good behaving in a way that scares someone with jealousy.
Halloween costumes are common to people who want to make their partner or ex-partner scare with jealousy in order to control them.
Consider the type of costume for additional meaning.
Example: A man dreamed of seeing someone wearing a Halloween mask. In waking life he was aware of himself needing fake his personality to scare other people into giving him money to deal with a problem.
Example 2: A man dreamed of being unable to find his Halloween costume. In waking life he was unable to find a way to scare his ex-girlfriend with jealousy in order to make her remain his girlfriend.