What is the term for a lateral movement of the horse?

The term that best describes a lateral movement of the horse is "amble." An amble is a specific gait characterized by a smooth, four-beat lateral movement, often seen in certain horse breeds. In this gait, the horse moves its legs on the same side in unison, which gives it a unique rhythm and enables a smooth, balanced motion that is preferred for comfort over long distances.

The other choices refer to different gaits that do not fit the description of lateral movement. The canter and gallop are both more rapid gaits where the horse progresses forward in a diagonal or jumping motion rather than a lateral one. The trot, while a two-beat gait, features a diagonal movement where a front leg and the opposite hind leg move together, rather than the lateral coordination characteristic of an amble. This distinguishing feature of ambling is what sets it apart from the other gaits mentioned.