The Collaborative International Dictionary of English v.0.48:

Constable \Con"sta*ble\ (k[o^]n"st[.a]*b'l or
   k[u^]n"st[.a]*b'l), n. [OE. conestable, constable, a
   constable (in sense 1), OF. conestable, F. conn['e]table, LL.
   conestabulus, constabularius, comes stabuli, orig., count of
   the stable, master of the horse, equerry; comes count (L.
   companion) + L. stabulum stable. See Count a nobleman, and
   Stable.]
   1. A high officer in the monarchical establishments of the
      Middle Ages.
      [1913 Webster]

   Note: The constable of France was the first officer of the
         crown, and had the chief command of the army. It was
         also his duty to regulate all matters of chivalry. The
         office was suppressed in 1627. The constable, or lord
         high constable, of England, was one of the highest
         officers of the crown, commander in chief of the
         forces, and keeper of the peace of the nation. He also
         had judicial cognizance of many important matters. The
         office was as early as the Conquest, but has been
         disused (except on great and solemn occasions), since
         the attainder of Stafford, duke of Buckingham, in the
         reign of Henry VIII.
         [1913 Webster]

   2. (Law) An officer of the peace having power as a
      conservator of the public peace, and bound to execute the
      warrants of judicial officers. --Bouvier.
      [1913 Webster]

   Note: In England, at the present time, the constable is a
         conservator of the peace within his district, and is
         also charged by various statutes with other duties,
         such as serving summons, precepts, warrants, etc. In
         the United States, constables are town or city officers
         of the peace, with powers similar to those of the
         constables of England. In addition to their duties as
         conservators of the peace, they are invested with
         others by statute, such as to execute civil as well as
         criminal process in certain cases, to attend courts,
         keep juries, etc. In some cities, there are officers
         called high constables, who act as chiefs of the
         constabulary or police force. In other cities the title
         of constable, as well as the office, is merged in that
         of the police officer.
         [1913 Webster]

   High constable, a constable having certain duties and
      powers within a hundred. [Eng.]

   Petty constable, a conservator of the peace within a parish
      or tithing; a tithingman. [Eng.]

   Special constable, a person appointed to act as constable
      of special occasions.

   To overrun the constable, or outrun the constable, to
      spend more than one's income; to get into debt. [Colloq.]
      --Smollett.
      [1913 Webster]