Spiritually a door represents the sheltering aspect of the Great Mother.
Psychological / Emotional Perspective:
If the door in the dream is shut or difficult to open, it indicates we are creating obstacles for ourselves, whereas if the door is open we can have the confidence to move forward.
Everyday Material Aspects:
A door in a dream signifies a movement between two states of being. It can represent entry into a new phase of life, such as puberty or middle age. There may be opportunities available to us about which we must make deliberate decisions.
Gender / Specific Meanings:
You might like to consult the entry for Door in Buildings.