thornback

plural thornbacks

1. Any animal with a thorny back, especially marine animals, such as:
   1. The thornback guitarfish (Platyrhinoidis triseriata), a species of ray in the north-eastern Pacific Ocean.
   2. The thornback ray or thornback skate (Raja clavata), a species of ray in the Atlantic Ocean.
   3. The thornback skate (Dentiraja lemprieri), a fish endemic to Australia.
2. archaicA woman over a certain age (variously 26 or 30) who has never married, older than a spinster.

   [A] society of honest gentlemen [is holding a lottery] for the benefit of all single ladies, widows, maids, or thornbacks […]

   1710, Isaac Bickerstaff (pseudonym), A Good husband for five shillings, or Esquire Bickerstaff's Lottery, quoted in 2016, Amy M. Froide, Silent Partners: Women As Public Investors During Britain's Financial Revolution, 1690-1750, Oxford University Press, page 46

   2 more examples

   Spinsters. — In a society where marriages were formed very early, girls often wedding at sixteen or under, […] At the age of thirty a spinster was called a "thornback ,” but bachelors and thornbacks were not the only people who […]

   1920, Anna Mary Galbraith, The Family and the New Democracy: A Study in Social Hygiene, page 184

   "And I'll be a thornback spinster! Oh, I'd rather die of the pox than that!" She bolted away to spill her bitter tears out of doors in a place where no one could observe her. Her bold adventure had suddenly turned against her.

   2009, Suzy Witten, The Afflicted Girls, →ISBN, page 131