A paper or plastic container (not necessarily a bag) used to package the leftovers of a diner's meal at a restaurant so that he or she may take it home to eat later. The servings here are so huge that I always have to ask for a doggy bag at the end of the night!
n. a bag—supplied by a restaurant—in which uneaten food can be carried home. We do not have doggy bags, but I can give you a styrofoam box. You must fill it yourself.