String along is a commonly used colloquialism that means to lead someone on, deceive or manipulate. There are several synonyms for the term depending on the context or the situation. In some cases, people might use words like fool, dupe, or trick as synonyms. Others might use words like lead, mislead, or deceive. In more formal settings, people might use words like beguile, seduce, or lure. Each of these words has a slightly different connotation, and their use will depend on the intent of the speaker and the context of the situation. Ultimately, whether it is cheating on someone or playing them for a fool, leading someone on is never a good thing to do.