The Collaborative International Dictionary of English v.0.48:
Vouchee \Vouch*ee"\, n. (Law) The person who is vouched, or called into court to support or make good his warranty of title in the process of common recovery. --Blackstone. [1913 Webster]WordNet (r) 3.0 (2006):
vouchee n 1: (law) a person called into court to defend a title