\Sei"zin\, n. [F. saisine. See {Seize}.] 1. (Law) Possession; possession of an estate of froehold. It may be either in deed or in law; the former when there is actual possession, the latter when there is a right to such possession by construction of law. In some of the United States seizin means merely ownership. --Burrill. 2. The act of taking possession. [Obs.] 3. The thing possessed; property. --Sir M. Halle. Note: Commonly spelt by writers on law seisin. {Livery of seizin}. (Eng. Law) See Note under {Livery}, 1.