Come on now, like you have never heard that before. It means that you are incredibly skinny. You are obviously malnutritioned, and if someone does not intervene you will be dead within a week.
I believe the Webster's dictionary definition is: A slang term for one who has experienced an abnormal amount skeletal muscle hypertrophy. This growth is more evident in the highly glycolytic Type II-b fibers, but can also be seen in the intermediate Type II-a fibers, as well as, the highly oxidative Type I fibers.
Sorry, I am a complete Smart A$$!!!!!