Resentment is read as an old grievance that has not been let go. Dream books see it as energy tied up in the past, inviting the dreamer to name the hurt and decide what to do with it.
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.