Real Dictionary

horse
When you talk about the horses, you mean horse races in which people bet money on the horse which they think will win.
countable noun: A horse is a large animal which people can ride. Some horses are used for pulling ploughs and carts.

horse in American English
a domesticated or wild, perissodactylous mammal (Equus caballus), raised in many breeds, having a large body and head, four usually long, thin legs, and a long, flowing tail: horses have been ridden, used to pull loads, etc. since ancient times
of a horse or horses
to mount or go on horseback
to supply with a horse or horses; put on horseback

horse in American Englishesp collectively
noun: a large, solid-hoofed, herbivorous quadruped, Equus caballus, domesticated since prehistoric times, bred in a number of varieties, and used for carrying or pulling loads, for riding, and for racing