Move back can be substituted for a variety of synonyms depending on the context and intention. One of the most common is "retreat," which refers to withdrawing or moving back from a position or situation. Another option is "recede," which implies a gradual movement away from a point or goal. Similarly, "backtrack" indicates a reversal of direction or action. "Withdraw" means to remove or take away oneself from a situation, often to avoid conflict. "Step backward" or "move in reverse" are literal alternatives for physically moving away from something or someone. Ultimately, the best synonym for move back will depend on the situation in which the phrase is being used.