noun
restive horse; runaway horse; uncontrollable horse
Refers to a horse that is difficult to control, often bucking or bolting. Can also be used figuratively for an unruly person.
暴れ馬に乗るのは危険だ。
Riding a restive horse is dangerous.
彼はまるで暴れ馬のような性格だ。
He has a personality like an unruly horse.