The Collaborative International Dictionary of English v.0.48:

Tory \To"ry\, n.; pl. Tories. [ Properly used of the Irish
   bogtrotters who robbed and plundered during the English civil
   wars, professing to be in sympathy with the royal cause;
   hence transferred to those who sought to maintain the extreme
   prerogatives of the crown; probably from Ir. toiridhe, tor, a
   pursuer; akin to Ir. & Gael. toir a pursuit.]
   1. (Eng. Politics) A member of the conservative party, as
      opposed to the progressive party which was formerly called
      the Whig, and is now called the Liberal, party; an earnest
      supporter of existing royal and ecclesiastical authority.
      [1913 Webster]

   Note: The word Tory first occurs in English history in 1679,
         during the struggle in Parliament occasioned by the
         introduction of the bill for the exclusion of the duke
         of York from the line of succession, and was applied by
         the advocates of the bill to its opponents as a title
         of obloquy or contempt. The Tories subsequently took a
         broader ground, and their leading principle became the
         maintenance of things as they were. The name, however,
         has for several years ceased to designate an existing
         party, but is rather applied to certain traditional
         maxims of public policy. The political successors of
         the Tories are now commonly known as Conservatives.
         --New Am. Cyc.
         [1913 Webster]

   2. (Amer. Hist.) One who, in the time of the Revolution,
      favored submitting to the claims of Great Britain against
      the colonies; an adherent to the crown.
      [1913 Webster]