What does "vavasor" mean?

Vavasor: The vassal or tenant of a baron; one who held under a baron, and who also had tenants under him; one in dignity next to a baron; a title of dignity next to a baron. Burrill. "A worthy vavasour." Chaucer. [Also written vavasour, vavassor, valvasor, etc.] Vavasours subdivide again to vassals, exchanging land and cattle, human or otherwise, against fealty. Motley.