The Collaborative International Dictionary
Cestuy que use
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.
Wiktionary
cestuy que use
n. (context legal English) A person for whose use land, etc., is granted to another.