Dictionary.com
definitions

heirdom

[air-duh m]
noun
  1. heirship; inheritance.

Origin of heirdom

First recorded in 1590–1600; heir + -dom
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for heirdom

heirdom

noun
  1. property law succession by right of blood; inheritance
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012