[su.zer.ain] n [F, fr. (assumed) MF suserain, fr. MF sus up (fr. L sursum, fr. sub- up + versum -ward, fr. neut. of versus, pp. of vertere to turn) + -erain (as in soverain sovereign)--more at sub-, worth] (1807) 1: a superior feudal lord to whom fealty is due: overlord
2: a dominant state controlling the foreign relations of a vassal state but allowing it sovereign authority in its internal affairs