springing executory interest

Noun

 * 1)  An interest in an estate in land created by the conditions of a grant wherein the grantor cuts short the grantor's own interest in the property in favor of the grantee, contingent upon the occurrence of a specific condition.
 * Joe gives land "to Harry, if Harry graduates from law school". Harry has a springing executory interest because his graduation from law school directly divests Joe of ownership.