Cestuy \Ces"tuy\ or Cestui \Ces"tui\, pron. [Norm. F.] (Law) He; the one. {Cestuy que trust}[norm. F.], a person who has the equitable and beneficial interest in property, the legal interest in which is vested in a trustee. --Wharton. {Cestuy que use}[Norm. F.], a person for whose use land, etc., is granted to another.