(1):

(n.) The grantee of a fief, feud, or fee; one who holds land of superior, and who vows fidelity and homage to him; a feudatory; a feudal tenant.

(2):

(v. t.) To treat as a vassal; to subject to control; to enslave.

(3):

(n.) A subject; a dependent; a servant; a slave.

(4):

(a.) Resembling a vassal; slavish; servile.