Definition - Noun [Anglo-French seisine, from Old French saisine act of taking possession, from saisir to seize, of Germanic origin] 1: the possession of land or chattels: as a: the possession of land arising from livery of seisin see also livery of seisin b: the possession of a freehold estate in land by one having title thereto 2: the right to immediate possession of an estate or to immediate succession <~ of an heir upon death of the testator> Pronunciation'sEz-n