The Collaborative International Dictionary of English v.0.48:

Rajah \Ra"jah\ (r[aum]"j[aum] or r[=a]"j[.a]), n. [Hind.
   r[=a]j[=a], Skr. r[=a]jan, akin to L. rex, regis. See
   Regal, a.]
   A native prince or king; also, a landholder or person of
   importance in the agricultural districts. [India]
   [1913 Webster]

WordNet (r) 3.0 (2006):

rajah
    n 1: a prince or king in India [syn: raja, rajah]