Source : Webster's Revised Unabridged Dictionary (1913)

Post \Post\, n. [F. poste, LL. posta station, post (where horses
   were kept), properly, a fixed or set place, fem. fr. L.
   positus placed, p. p. of ponere. See {Position}, and cf.
   {Post} a pillar.]
   1. The place at which anything is stopped, placed, or fixed;
      a station. Specifically:
      (a) A station, or one of a series of stations, established
          for the refreshment and accommodation of travelers on
          some recognized route; as, a stage or railway post.
      (b) A military station; the place at which a soldier or a
          body of troops is stationed; also, the troops at such
          a station.
      (c) The piece of ground to which a sentinel's walk is
          limited.

   2. A messenger who goes from station; an express; especially,
      one who is employed by the government to carry letters and
      parcels regularly from one place to another; a letter
      carrier; a postman.

            In certain places there be always fresh posts, to
            carry that further which is brought unto them by the
            other.                                --Abp. Abbot.

            I fear my Julia would not deign my lines, Receiving
            them from such a worthless post.      --Shak.

   3. An established conveyance for letters from one place or
      station to another; especially, the governmental system in
      any country for carrying and distributing letters and
      parcels; the post office; the mail; hence, the carriage by
      which the mail is transported.

            I send you the fair copy of the poem on dullness,
            which I should not care to hazard by the common
            post.                                 --Pope.

   4. Haste or speed, like that of a messenger or mail carrier.
      [Obs.] ``In post he came.'' --Shak.

   5. One who has charge of a station, especially of a postal
      station. [Obs.]

            He held office of postmaster, or, as it was then
            called, post, for several years.      --Palfrey.

   6. A station, office, or position of service, trust, or
      emolument; as, the post of duty; the post of danger.

            The post of honor is a private station. --Addison.

   7. A size of printing and writing paper. See the Table under
      {Paper}.

   {Post and pair}, an old game at cards, in which each player a
      hand of three cards. --B. Jonson.

   {Post bag}, a mail bag.

   {Post bill}, a bill of letters mailed by a postmaster.

   {Post chaise}, or {Post coach}, a carriage usually with four
      wheels, for the conveyance of travelers who travel post.
      

   {Post day}, a day on which the mall arrives or departs.

   {Post hackney}, a hired post horse. --Sir H. Wotton.

   {Post horn}, a horn, or trumpet, carried and blown by a
      carrier of the public mail, or by a coachman.

   {Post horse}, a horse stationed, intended, or used for the
      post.

   {Post hour}, hour for posting letters. --Dickens.

   {Post office}.
      (a) An office under governmental superintendence, where
          letters, papers, and other mailable matter, are
          received and distributed; a place appointed for
          attending to all business connected with the mail.
      (b) The governmental system for forwarding mail matter.

   {Postoffice order}. See {Money order}, under {Money}.

   {Post road}, or {Post route}, a road or way over which the
      mail is carried.

   {Post town}.
      (a) A town in which post horses are kept.
      (b) A town in which a post office is established by law.
          

   {To ride post}, to ride, as a carrier of dispatches, from
      place to place; hence, to ride rapidly, with as little
      delay as possible.

   {To travel post}, to travel, as a post does, by relays of
      horses, or by keeping one carriage to which fresh horses
      are attached at each stopping place.

Source : WordNet®

post horn
     n : wind instrument used by postilions of the 18th and 19th
         centuries