The Collaborative International Dictionary of English v.0.48:

Shah \Shah\ (sh[aum]), n. [Per. sh[=a]h a king, sovereign,
   prince. Cf. Checkmate, Chess, Pasha.]
   A former title of the supreme ruler in certain Eastern
   countries, especially Persia and Iran. [Written also
   schah.]
   [1913 Webster +PJC]

   Shah Nameh. [Per., Book of Kings.] A celebrated historical
      poem written by Firdousi, being the most ancient in the
      modern Persian language. --Brande & C.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Shah
    n 1: title for the former hereditary monarch of Iran [syn:
         Shah, Shah of Iran]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "shah":
   Dalai Lama, Holy Roman Emperor, Inca, Kaiser, ardri, bey, cacique,
   caesar, cham, czar, kaid, khan, mikado, negus, padishah, pendragon,
   pharaoh, rig, sachem, sagamore, sheikh, shogun, tenno, tycoon