Being wise to someone can be expressed in various ways. One of the synonyms for this phrase is to "be onto someone." It means that you are aware of someone's actions or motives and are ready to take action if needed. Another synonym for being wise to someone is "being in the know." This phrase implies that you have access to information that others may not have and are aware of what is going on at all times. Another synonym for being wise to someone is "being hip." This slang term refers to being well-informed and aware of current trends and happenings, making you an expert in the subject. All of these synonyms convey the idea that you are wise, knowledgeable, and aware of your surroundings.