Fig. to make one's case primarily to one's supporters; to make one's case only to those people who are present or who are already friendly to the issues. There is no need to convince us of the value of hard work. We already know that. You are just preaching to the choir. Don't waste your time telling us about the problem. That's preaching to the choir. Bob found himself preaching to the converted when he was telling Jane the advantages of living in the suburbs. She already hates city life.