horse: the animal, above all the war-horse ridden or driven into battle
This word simply means "horse," and every place it appears it names the animal itself. There is no hidden second sense to untangle. What a reader does need to feel is what a horse meant to people in the biblical world, because it was not the farm animal or family pet it can be for us.
In the ancient Near East the horse was first and last a machine of war. Common transport and farm work were done by the donkey and the ox; the horse pulled the chariot and carried the cavalryman. So to picture a horse was to picture military power, speed, and the might of empires. That background runs under nearly every use here. The horse is the mount of conquest, of armies, and of judgment.
Most occurrences fall in the visions of Revelation, where horses carry riders who bring conquest, war, famine, and death, where a rider called Faithful and True goes out on a white horse, and where the birds are summoned to feast on the flesh of horses and their riders. Even the strange locust-creatures of one vision are described as looking like horses ready for battle. Set against these war-horses is the single plain, everyday example: the small bit put in a horse's mouth to turn its whole body, used as a picture of how a small thing can steer something large.