* Different categories: A horse is an animal, so you can't really have an opposite in terms of a different animal type.
* Specific traits: You could think about specific traits of horses and their opposites:
* Large: Small (but this would apply to many animals)
* Hooves: Paws (again, many animals have paws)
* Equine: Bovine (but this is just another animal type)
Instead of an opposite, you might think about:
* Contrasting animals: You could compare a horse to a dog, a cat, a bird, etc.
* Specific contexts: If you're looking for an opposite within a particular context, you might be able to find something more relevant. For example, in a race, the opposite of a horse might be a runner.
Ultimately, the "opposite" of a horse is very context-dependent and may not have a single definitive answer.