"Run that by me again" is a phrase used to request clarification or repetition of what someone has just said. There are several synonyms you can use to convey the same meaning. One is "Can you repeat that?" which is a direct request for someone to say something again. Another synonym is "I didn't quite catch that," which is more of a polite way of asking someone to clarify what they have just said. You can also use "Could you please rephrase that?" or "Pardon me, could you repeat that slower?" to get them to elaborate or explain more slowly. All of these alternatives can help you communicate effectively and ensure you fully understand what the other person is saying.