M.D. stands for Medical Doctor and is a professional designation for someone who has completed medical school and is licensed to practice medicine. A Doctor of Medicine (M.D.) is a physician who diagnoses and treats diseases, prescribes medications, and performs medical procedures. The two crossword solutions, DOC and PHYS, are abbreviations for Doctor of Medicine and Physician, respectively. Both terms refer to the same profession, but are used interchangeably in different contexts.