The ownership of property; The possession of an estate of freehold. It is both ownership and possession. It is legal possession of a feudal fiefdom or an estate in land. This is an old term that originated during the feudal ages when the King of England owned the land in England and his subjects held tenures in fiefs. The term seisin appears in deeds drafted many years ago and has not been used in real estate transactions in the modern era.
SEISIN
TheLaw.com Law Dictionary & Black's Law Dictionary 2nd Ed.