Definition of Executory Devise
Devise of a future estate, and, if the executory devisee dies before the event happens, the estate goes to the heir at the time of the event, and not to the heir at the time of the death of the devisee. The happening of the contingency determines who is to take the estate, and until that time no one has an interest to transmit. By the earlier common law it was an established rule that a devise of lands, without words of limitation, conferred upon the devisee an estate for life only. An exception was soon recognized in the case of a will, so that an estate in fee could be given without the use of the technical words required in a conveyance or deed. The gift in such case was known as an "executory devise.”
That's the definition of Executory Devise in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.
