Executory-interest meaning

(law) An third party interest in an estate in land created by the conditions of a grant wherein the grantor gives the land to a second party, but with said land going to a third party upon the occurrence of a condition; an interest created subject to a fee simple subject to executory interest.

Joe gives land "to Mike, but if Harry graduates from law school, to Harry". Harry has an executory interest which he can realize by graduating from law school; Mike owns the land subject to Harry's executory interest.