SEISIN Meaning of SEISIN in English [ 'si:zɪn ](also seizin ) ■ noun Law possession of land by freehold. ↘ Brit. historical possession, especially of land.OriginME: from OFr. ~e , from saisir 'seize'. Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004