What is Contingent Estate?

Legal Definition
A contingent estate depends for its effect upon an event which may or may not happen: as an estate limited to a person not in esse or not yet born. Crabb on Real Property, b. 3, c. 1, sect. 2. 946.
-- Bouviers Law Dictionary
Legal Definition
An estate which depends for its effect upon an event which may or may not happen; as an estate limited to a person not in esse, or not yet bom. 2 Crabb, Real Prop. p. 4, ยง 946; Haywood v. Shreve, 44 N. J. Law, 94; Wadsworth v. Murray, 29 App. Div. 191, 51 N. Y. Supp. 1038; Thornton v. Zea, 22 Tex. Civ. App. 509, 55 S. W. 798; Hopkins v. Hopkins, 1 Hun, 354.
-- Black's Law Dictionary
Legal Definition
One wherein the person who is to enjoy it, or the event upon which it is to arise, is uncertain. See 185 Pa. St. 179, 64 Am. St. Rep. 621, 39 Atl. 879; 64 Am. St. Rep. 658, note.
-- Ballentine's Law Dictionary