1. Literally, having a larger bone structure than the average of one's demographic. Some people are naturally big boned, offering them a broader frame or greater height than others. It is often the big-boned men and women of the family who work the farm.
2. A euphemism for being fat or obese, usually used as an excuse for one's size. I know that people think I have an eating problem, but really I'm just big boned!