A rude gesture says without words what politeness keeps back. Dream books read it as contempt or defiance looking for a way out, whether it is aimed at you or comes from your own hand.
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.