A guy calling you a snack might indicate that he likes you, which is more likely if he exclusively says it to you and exhibits other signals of attraction around you. He may have have been kidding, attempting to cheer you up, or just watching your reaction. If he never calls anyone else a snack, then he really was being serious. Snacks are usually junk food that people eat between meals, so if a guy calls you one, he probably doesn't think much of you at all. This phrase is often used as a derogatory term. So don't take it too seriously. Snacks generally have little nutritional value and can be quite unhealthy. Also see: meaning of snack.