Shiah US/ˈʃiʌ/ uncommon noun 1. one of the two main branches of orthodox Islam; mainly in Iran SynonymsShiaShiah Islamthe Shiites Related words Word family Shiah Islam Broader terms sect Parts Islam Part of Shiite WordNet 2.1 (Princeton University). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved.