Mare

A mare is an adult female horse or other equine.

In most cases, a mare is a female horse over three, and a filly is a female horse three and younger. In Thoroughbred horse racing, a mare is defined as a female horse more than four years old, but the word can also be used for other female equine animals, particularly mules and zebras, but a female donkey is usually called a "jenny." A broodmare is a mare used for breeding. A horse's female parent is known as its dam.

An uncastrated adult male horse is called a stallion and a castrated male is a gelding. Occasionally, the term "horse" is used to designate only a male horse.

https://en.wikipedia.org/wiki/Mare