There are many different ways to describe someone who is riding on a horse. You might say they are on horseback, astride a horse, or seated in the saddle. Other options include mounted on a horse, perched on a steed, or trotting on horseback. If the horse is particularly strong or powerful, you could describe the rider as gripping the reins or holding tight to the horse's mane. Whether you are writing a story, describing a scene in a movie, or simply talking about someone riding a horse, there are many different synonyms and ways to convey the excitement and thrill of horseback riding.