any old costume is not DRAG man, Drag is specifically dressing as your opposite gender. (unless you are genderneutral, gender fluid, genderless, or just a eunuch.....hahahahhahha)
wearing a uniform is not drag.
dressing to fit the occassion (business suit) is not drag.
maybe in purely general (hence vague and inapplicable to any specific instance) terms one could see any form of dress and costume as drag, but that would be like seeing any form of religious worship as satanism, or Lutheranism....