1.(in the feudal system) a person granted the use of land, in return for rendering homage, fealty, and usually military service or its equivalent to a lord or other superior; feudal tenant.
2.a person holding some similar relation to a superior; a subject, subordinate, follower, or retainer.
3.a servant or slave.
c.1300 (implied in vassalage ) "tenant who pledges fealty to a lord," from O.Fr. vassal, from M.L. vassallus "manservant, domestic, retainer," from vassus "servant," from O.Celt. *wasso- "young man, squire" (cf. Welsh gwas "youth, servant," Bret. goaz "servant, vassal, man," Ir. foss "servant"). The adj. is recorded from 1593.