An unfamiliar symbol is read as a message from the unconscious, still waiting to be decoded. Tradition sees it as meaning that is felt before it can be put into words.
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.