Neither one floor nor the next, the mezzanine stands for an in-between position — partly involved, partly watching. Dream books read it as a halfway stage in some climb or change.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.