A mill grinds grain into flour, and dream books read it as steady work turning raw effort into something useful. The turning wheel also stands for the passage of time and the routine of daily life.
When this appeared in your dream, what were you feeling?
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.