WordNet (r) 3.0 (2006):

ijtihad
    n 1: the endeavor of a Moslem scholar to derive a rule of divine
         law from the Koran and Hadith without relying on the views
         of other scholars; by the end of the 10th century
         theologians decided that debate on such matters would be
         closed and Muslim theology and law were frozen; "some
         reform-minded Islamic scholars believe that reopening
         ijtihad is a prerequisite for the survival of Islam"