An expression used when one remembers or realizes something because of what the other person has just said. An abbreviated form of the full phrase "now that you have come to mention it." A: "The weather's been a bit unpredictable lately, huh?" B: "Come to mention it, I hear there could be a blizzard next week." A: "I hate filling out these tax forms." B: "Come to mention it, I don't think I ever filed my taxes last year!"