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

The Collaborative International Dictionary of English v.0.48:

Moghul \Mo*ghul"\, Mogul \Mo*gul"\, prop. a. [See Mogul, n..]
   Of or pertaining to the Moguls[2]; as, The Taj Mahal, the
   most beautiful piece of Mogul architecture, was built by the
   Mogul emperor Shah Jehan as a mausoleum for his favorite
   wife.
   [PJC] Moghul empire

WordNet (r) 3.0 (2006):

mogul
    n 1: a bump on a ski slope
    2: a member of the Muslim dynasty that ruled India until 1857
       [syn: Mogul, Moghul]
    3: a very wealthy or powerful businessman; "an oil baron" [syn:
       baron, big businessman, business leader, king,
       magnate, mogul, power, top executive, tycoon]

Moby Thesaurus II by Grady Ward, 1.0:

93 Moby Thesaurus words for "mogul":
   Establishment, VIP, avalanche, baron, big cheese, big gun, big man,
   big name, big noise, big shot, big wheel, bigwig, blizzard, brass,
   brass hat, celebrity, crystal, czar, dignitary, dignity,
   driven snow, elder, father, figure, flake, flurry, granular snow,
   great man, hotshot, igloo, important person, interests, king, lion,
   lords of creation, magnate, man of mark, mandarin, mantle of snow,
   merchant prince, nabob, name, notability, notable, panjandrum,
   person of renown, personage, personality, pillar of society, power,
   power elite, prince, ruling circle, sachem, slosh, slush, snow,
   snow banner, snow bed, snow blanket, snow blast, snow fence,
   snow flurry, snow roller, snow slush, snow squall, snow wreath,
   snow-crystal, snowball, snowbank, snowbridge, snowcap, snowdrift,
   snowfall, snowfield, snowflake, snowland, snowman, snowscape,
   snowshed, snowslide, snowslip, snowstorm, somebody, something,
   the great, the top, top brass, top people, tycoon,
   very important person, wet snow, worthy