Bigorexia is an everyday term for muscle dysmorphia, a disorder in which people become obsessed with muscle-building. The term was presumably a back-formation from anorexia, since they're seen as opposites--anorexics want to be smaller and thinner, while bigorexics want to be bigger and stronger. (If one were to be a linguistic purist about it, bigorexia would mean "big eater" or "big appetite.") Bigorexics often end up taking steroids and spending all their time in the gym, which (paradoxically) can end up causing them injury and shrinking their muscles in the long run. Like anorexics, bigorexics have a distorted view of their own appearance--people in the throes of bigorexia are often enormous to the point of being musclebound, while anorexics are often thin to the point of emaciation.