freemartin

Late 17th century. Etymology unknown.

freemartin (plural freemartins)

1. A female calf, born as twin with a bull calf, but sexually imperfect (often infertile).
2. Any female animal born sterile or otherwise infertile.

   "Has your cat been spayed?" "I didn't need to: she's a freemartin."

• Webster's Seventh New Collegiate Dictionary, Springfield, Massachusetts, G.&C. Merriam Co., 1967

• interframe