Totally confident in or convinced of someone's or something's viability, veracity, appropriateness, skill, etc. I don't know, this plan still sounds pretty risky to me—I'm not sold on it yet. After seeing the presentation, I'm sold on this investment—let's go for it! A: "What do you think about the new quarterback?" B: "He's someone who's supposed to be the best in the league, but I'm not sold on him yet."