What do you call an uncastrated male horse that is at least 4 years old?

An uncastrated male horse that is at least 4 years old is referred to as a stallion. Stallions are male horses that have not undergone castration, allowing them to retain their reproductive capabilities. They are usually distinguished by their physical maturity and behavior, as they can display more aggressive and dominant traits compared to geldings (castrated males).

In the context of equine terminology, a colt typically refers to a male horse that is under 4 years of age, which means that it would not apply here since the horse in question is older. A gelding is a male horse that has been castrated, thus it cannot be the correct answer since the horse is uncastrated. Lastly, a filly refers to a young female horse, which again does not relate to the question about an uncastrated male horse. Therefore, the term stallion accurately describes a mature, intact male horse that is at least 4 years old.