What's a mare?

Is this a stallion or a mare?

According to the novel Agnes Grey by Anne Brontë, it was considered unladylike to call a horse a mare.

But soon their skins turned cold, for there came a sound of galloping across the moor, and the black mare, dabbled with white froth, went past with trailing bridle and empty saddle.

I cannot moo like a cow. I'm a mare!

Marek sprained his wrist.

Sami's favorite mount was a mare named Layla.

Is your name Marek?

If the car breaks down, I’ll have to go by shank’s mare.

My mare is white.