Source : Webster's Revised Unabridged Dictionary (1913)

Orderly \Or"der*ly\, a.
   1. Conformed to order; in order; regular; as, an orderly
      course or plan. --Milton.

   2. Observant of order, authority, or rule; hence, obedient;
      quiet; peaceable; not unruly; as, orderly children; an
      orderly community.

   3. Performed in good or established order; well-regulated.
      ``An orderly . . . march.'' --Clarendon.

   4. Being on duty; keeping order; conveying orders.
      ``Aids-de-camp and orderly men.'' --Sir W. Scott.

   {Orderly book} (Mil.), a book for every company, in which the
      general and regimental orders are recorded.

   {Orderly officer}, the officer of the day, or that officer of
      a corps or regiment whose turn it is to supervise for the
      day the arrangements for food, cleanliness, etc. --Farrow.

   {Orderly room}.
      (a) The court of the commanding officer, where charges
          against the men of the regiment are tried.
      (b) The office of the commanding officer, usually in the
          barracks, whence orders emanate. --Farrow.

   {Orderly sergeant}, the first sergeant of a company.

Source : WordNet®

orderly sergeant
     n : the first sergeant of a company; duties formerly included
         the conveyance of orders