Can you defrost in a microwave a carton of milk that was kept in the freezer?

you could, but i would not recommend. microwave defrosting heats the item briefly and then takes the heat away over and over. I'd be worried that the milks taste or consistency or freshness may suffer form this. I'd rather you sit the milk in a huge pot of room temp water and change it frequently, or just be patient and let it thaw over night in the fridge.