A rider without a head stands for drive without direction — momentum that has lost its thinking part. Dream books read it as being swept along by fear or habit rather than choice.
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.