The Collaborative International Dictionary of English v.0.48:

Mollah \Mol"lah\, n. [Ar. maul[=a], commonly moll[=a]in Turkey.]
   1. One of the higher order of Turkish; also, a Turkish title
      of respect for a religious and learned man. [Written also
      mullah and moolah.]
      [1913 Webster +PJC]

   2. A title of respect used in Islamic countries for one who
      is learned in Islamic law; a teacher or expounder of
      Islamic law.
      [PJC]

WordNet (r) 3.0 (2006):

Mollah
    n 1: a Muslim trained in the doctrine and law of Islam; the head
         of a mosque [syn: Mullah, Mollah, Mulla]