A garbage disposal grinds away leftovers, so tradition reads it as getting rid of what is no longer useful. It can also reflect a fear of something important being lost by accident.
Does the traditional reading fit your dream, or did it mean something else to you?
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.