To convert into a feudal system; to establish feudal relationships and structures of power in a society or region. (British spelling)
From 'feudal' plus the verb suffix '-ise' (British) or '-ize' (American), allowing the adjective to function as a verb meaning to make feudal.
Feudalise is rarely used in modern English because feudalism itself is mostly history—but historians use it when describing how scattered warring kingdoms gradually organized into feudal structures!
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