WordNet records no synonym and no antonym for ijtihad. It is the only member of its synset, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
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”
Synonyms, antonyms and the broader and narrower relations for ijtihad come from Princeton University’s WordNet. Full sources and licences.