Montfort mont·fort US/ˈmɑntfɜrt/ uncommon noun 1. an English nobleman who led the baronial rebellion against Henry III (1208-1265) SynonymsSimon de MontfortEarl of Leicester Related words Broader terms Earl WordNet 2.1 (Princeton University). CMU Pronouncing Dictionary. WordNet 2.1 Copyright Princeton University. All rights reserved.