Webster's Revised Unabridged Dictionary · 1913

Mortmain

Mortmain , noun

[French mort, morte, dead + main hand; French main-morte. See Mortal, and Manual.]

(Law) Possession of lands or tenements in, or conveyance to, dead hands, or hands that cannot alienate.

The term was originally applied to conveyance of land made to ecclesiastical bodies; afterward to conveyance made to any corporate body.