The Collaborative International Dictionary of English v.0.48:

Mogul \Mo*gul"\, n. [From the Mongolian.]
   1. A person of the Mongolian race.
      [1913 Webster]

   2. Specifically: Any of the Mongolian peoples who conquered
      parts of India and established an empire lasting from 1526
      to 1857. Also, any of their descendents.
      [PJC]

   3. (Railroad) A heavy locomotive for freight traffic, having
      three pairs of connected driving wheels and a two-wheeled
      truck.
      [1913 Webster]

   4. A great personage; magnate; autocrat; as, an industrial
      mogul.
      [Webster 1913 Suppl.]

   Great Mogul, or Grand Mogul, the sovereign of the empire
      founded in Hindustan by the Mongols under Baber in the
      sixteenth century. Hence, a very important personage; a
      lord; -- sometimes only mogul or Moghul. --Dryden.
      [1913 Webster] Moghul