one of the highest British orders of chivalry. Its full name is the Most Ancient and Most Noble Order of the Thistle. People who are appointed to the order may put the letters KT or LT (meaning Knight of the Thistle or Lady of the Thistle) after their names. The order was started in 1687 and is mainly for members of the Scottish peerage. The thistle, a prickly plant, is the national emblem of Scotland.