In general having a dream in which a mirror was prominently featured has always been considered to be a powerful omen. The actual meaning of the dream however is variable and it depends strongly on the circumstances in it.
Simply seeing a mirror in your dream signifies that you will soon have notable change in your life that will affect both the personal and professional spheres of your life. If this dream is of recurring nature it can signify that you will have very significant and fundamental changes in your life in a short period of time.
Seeing a mirror that is old, tarnished or cracked means that you in the near future you will try to change your appearance. Sometimes, this dream can point to the dreamer not being happy with their present physical appearance.
If in the dream you simply look into a mirror the meaning can be variable depending what you will see in the mirror. If you see yourself than it means that someone will insult you in the upcoming time. Seeing other person that you know in the mirror means that the said person behaves in a unfair manner towards you. If in the mirror you see people that are unknown to you than it means that soon you will meet a very interesting person that will have similar inclinations to yours. Seeing fire and flames in the mirror, points to unsatisfied desires in your life.
According to other interpretations seeing one of your friends in a mirror can mean that they are not completely honest with you. They might be insincere and quite hypocritical in their attitudes.
If in the dream you look in a mirror and you don’t see any reflection that it means that you have great inner piece within you. If this dream is of reoccurring nature than it can mean that you are in a middle of great spiritual journey.