A dinner winner is a guy you won't date but you will bring home to mom. He's a nice guy, the kind of guy your mom wants you to date. He's the kind of guy you might bring to a family wedding or thanksgiving to allay your parents' fears that you're a total lesbo. Hence he gets a lot of dinners out of knowing you. In its more pejorative sense, a dinner winner is a loser. He's the opposite of the typical bad boy all girls want to date between the ages of 14 and 28.