Fief/fiːf/ Definition 1 of 2Pro Tip 1/3Medieval Context Fief is closely linked to medieval history, relating to nobility and land. He studied how the fief system shaped medieval society. Pro Tip 2/3Service Exchange A fief involved an agreement of service, typically military, for land tenure. The warrior received a fief for his service to the king. Pro Tip 3/3Historical Feudalism Fief is a term from feudal systems where society was structured in hierarchies. Under feudalism, serfs worked on the lord's fief.