A wide, flat plain is read as openness, simplicity and a clear view in every direction. Folk tradition also links it to exposure, and to a long stretch of life without landmarks.
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.