The Collaborative International Dictionary of English v.0.48:

Ulema \U`le*ma"\, n. [Turk. & Ar. 'ulam[=a] the wise or learned
   men, pl. of '[=a]lim wise, learned, fr. alima to know.]
   (Islam)
   A college or body composed of the hierarchy (the imams, or
   ministers of religion, the muftis, or doctors of law, and the
   cadis, or administrators of justice). That of Turkey alone
   now has political power; its head is the sheik ul Islam.

   Note: This definition was written ca. 1900. The government of
         Turkey in 1998 is exclusively secular, whereas Iran in
         2001 is dominated by Moslem clergy.
         [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

ulema
    n 1: the body of Mullahs (Muslim scholars trained in Islam and
         Islamic law) who are the interpreters of Islam's sciences
         and doctrines and laws and the chief guarantors of
         continuity in the spiritual and intellectual history of the
         Islamic community [syn: ulema, ulama]