Subinfeudation is a practice in feudal systems where a vassal, who has received land from a lord, grants part of that land to a subordinate vassal in exchange for loyalty or services. This creates a hierarchy of land ownership and obligations, where the original lord retains ultimate ownership rights. This system allows for the distribution of land and the establishment of multiple layers of feudal relationships. It was common in medieval Europe and played a significant role in the organization of society and governance during that period.