A vassal[1] or liege subject[2] is a person regarded as having a mutual obligation to a lord or monarch, in the context of the feudal system in medieval Europe and elsewhere.
vassal state: a state with varying degrees of independence in its internal affairs but dominated by another state in its foreign affairs and potentially wholly subject to the dominating state
vassal state: a state with varying degrees of independence in its internal affairs but dominated by another state in its foreign affairs and potentially wholly subject to the dominating state
https://www.merriam-webster.com/dictionary/vassal state
took it for a typo at first, sorry