A scrubbing brush is read as hard effort to remove what is stubborn — a stain on the past or a habit that sticks. Scrubbing in vain traditionally reflects guilt that will not wash out.
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.