peeress

peer +‎ -ess

peeress (plural peeresses)

1. A noblewoman married to a peer.
   • 1863, Sheridan Le Fanu, The House by the Churchyard

     But there were more than a score of peers there beside, with their peeresses in tall feathers, diamonds, and monstrous hoops.

2. A woman holding a noble title in her own right.
   • 1892, Sir Arthur Conan Doyle, “The Noble Bachelor”, in The Adventures of Sherlock Holmes‎, HTML edition, The Gutenberg Project, published 2011:

     … it is obvious that the Californian heiress is not the only gainer by an alliance which will enable her to make the easy and common transition from a Republican lady to a British peeress.

• seepers