What is Escheat?

Legal Definition
Escheat /sˈt/ is a common law doctrine that transfers the property of a person who dies without heirs to the crown or state. It serves to ensure that property is not left in "limbo" without recognized ownership. It originally applied to a number of situations where a legal interest in land was destroyed by operation of law, so that the ownership of the land reverted to the immediately superior feudal lord.
-- Wikipedia
Legal Definition
Title to lands. According to the English law, escheat denotes an obstruction of the course of descent, and a consequent determination of the tenure, by some unforeseen contingency; in which case the land naturally results back, by a kind of reversion, to the original grantor, or lord of the fee.. 2 Bl. Com. 244.

2. All escheats, under the English law, are declared to be strictly feudal, and to import the extinction of tenure. Wright on Ten. 115 to 117; 1 Wm. Bl. R. 123.

3. But as the feudal tenures do not exist in this country, there are no private persons who succeed to the inheritance by escheat. The state steps in, in the place of the feudal lord, by virtue of its sovereignty, as the original and ultimate proprietor of all the lands within its jurisdiction. 4 Kent, Com. 420. It seems to be the universal rule of civilized society, that when the-deceased owner has left no heirs, it should vest in the public, and be at the disposal of the government. Code, 10, 10, 1; Domat, Droit Pub. liv. 1, t. 6, s. 3, n. 1. Vide 10 Vin. Ab. 139; 1 Bro. Civ. Law, 250; 1 Swift's Dig. 156; 2 Tuck. Blacks. 244, 245, n.; 5 Binn. R. 375; 3 Dane's Ab. 140, sect. 24; Jones on Land Office Titles in Penna. 5, 6, 93. For the rules of the Roman Civil Law, see Code Justinian, book 10.
-- Bouviers Law Dictionary
Legal Definition
In feudal law. Escheat is an obstruction of the course of descent, and consequent determination of the tenure, by some unforeseen contingency, in which case the land naturally results back, by a kind of reversion, to the original grantor or lord of the fee. 2 Bl. Comm. 15; Wallace v. Harm-stad, 44 Pa. 501; Marshall v. Lovdass, 1 N. C. 445. ' It is the casual descent, in the nature of forfeiture, of lands and tenements within his manor, to a lord, either on failure of issue of the tenant dying seised or on account of the felony of such tenant. Jacob. Also the land or fee itself, which thus fell back to the lord. Such lands were called "excadentim," or "terrae excadentiales." Fleta, lib. 6, c. 1; Ch Litt. 13a. In American law. Escheat signifies a reversion of property to the state in consequence of a want of any individual competent to inherit. The state is deemed to occupy the place and hold the rights of the feudal lord. See 4 Kent, Comm. 423, 424. Hughes v. State, 41 Tex. 17; Crane v. Reeder, 21 Mich. 70, 4 Am. Rep. 430; Civ. Code Ga. 1895, § 3575. "Escheat at feudal law was the right of the lord of a fee to re-enter upon the same when it became vacant by the extinction of the blood of the tenant. This extinction might either be per defectum sanguinis or else per delictum tenentis, where the course of descent was broken by the corruption of the blood of the tenant. As a fee might be holden either of the crown or from some inferior lord, the escheat was not always to the crown. The word 'escheat,' in this country, at the present time, merely indicates the preferable right of the state to an estate left vacant, and without there being any one in existence able to make claim thereto." 29 Am. Dec. 232, note.
See also
-- Black's Law Dictionary
Legal Definition
The reversion of title to the lord upon failure of heirs of the tenant to inherit; the reversion of land to the state upon failure of heirs. See 12 L. R. A. 529, note.
-- Ballentine's Law Dictionary
Legal Definition
The passing of an interest in land to the state when a decedent has no heirs or devisees.