noun
(historical, law) The grantee of a fief, a subordinate granted use of a superior's land and its income in exchange for vows of fidelity and homage and (typically) military service.
(historical) Any direct subordinate bound by such vows to a superior.
(figurative) Any subordinate bound by similar close ties.
adjective
Resembling a vassal; slavish; servile.
verb
(transitive) To treat as a vassal or to reduce to the position of a vassal; to subject to control; to enslave.
(transitive) To subordinate to someone or something.