A black hole is read as something that draws everything in and gives nothing back: a worry, a habit or a situation that consumes energy. It also stands for the mystery of what lies beyond the known.
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.