Wiktionary
n. A female calf, born as twin with a bull calf, but sexually imperfect (often infertile).
Wikipedia
A freemartin or free-martin (sometimes martin heifer) is an infertile female mammal with masculinized behavior and non-functioning ovaries. Genetically the animal is chimeric: Karyotyping of a sample of cells shows XX/XY chromosomes. The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas: an example of microchimerism. Externally, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-Müllerian hormone from the male twin. Freemartinism is the normal outcome of mixed-sex twins in all cattle species that have been studied, and it also occurs occasionally in other mammals including sheep, goats and pigs.
Usage examples of "freemartin".
Then came the silky-green freemartin Alsebra, a newcomer to the 109th Marneri Dragons.
The freemartin was formidably well-informed and, they feared, more intelligent than any of them.
The green freemartin was too lightly built to stand against this thing, and her sword could not cut the outer layer of the cataphragm.
Wynelda, a lively freemartin in the Kadein 144th was killed as a spear passed clean through her upper body.
Costa Rica days who knew a woman who knew a man who had a freemartin neuter companion who had formerly belonged to someone high up in the Census Department.
In fact, the wounded beast was Kasaset, a freemartin in the 66th dragons.
Even Alsebra, the caustic freemartin, had been subdued ever since the loss of the Broketail leather-back and his worthless dragonboy, Relkin.
Alsebra, the green freemartin renowned for her skill with dragonsword.
She knew that he did his best, but freemartins were inclined to be snappish, sulky, and short-tempered.
The most sensitive thing to any infertile female dragon, known as freemartins, was her lack of eggs.
Bryon, a golden-haired new face from Seant who handled Alsebra the freemartin.
But every dragon know that one in three sprats from a leatherback and green mating will be freemartin.