mortmains

Noun

mortmain (usually uncountable, plural mortmains)

1. (usually) The perpetual, inalienable possession of lands by a corporation or non-personal entity such as a church.
   • [W]e do hereby grant our especial license and authority unto all and every person […] to grant sell alien and convey in mortmain unto and to the use of the said Society and their successors […]1824, Charter of Incorporation of the Royal Asiatic Society of Great Britain and Ireland
2. (literary, usually) A strong and inalienable possession.
   • […]; and some part of that influence [of the government], which would otherwise have been possessed as in a sort of mortmain and unalienable domain, returned again to the great ocean from whence it arose, […]1770, Edmund Burke, Thoughts on the Present Discontents, and Speeches