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.