An atheist in a dream is read as doubt, independence of mind and questions about meaning. It may reflect your own scepticism or a conversation with belief you have not finished.
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.