"Crazy horse" is a phrase that can be used to refer to someone or something that is erratic, unpredictable, or difficult to control. Synonyms for this phrase include "wild horse," "unruly stallion," or even "untamed colt." Other synonyms might include "crazed animal," "mad beast," or "insane equine." Regardless of the specific wording used, these synonyms all point towards the same idea - that what is being described is something that is difficult to handle or control, with a tendency to behave in unexpected or dangerous ways. Similar terms could also include "frantic mustang," "unpredictable charger," or "uncontrollable bronco".