horseback

马背多用于 on horseback

The guards patrolled the border on horseback for hours.

警卫骑著马在边境巡逻了好几个小时。

骑马的限定用法

We signed up for a horseback tour through the valley.

我们报名参加了穿越山谷的骑马行程。

骑著马美式

She learned to ride horseback when she was seven.

她七岁就学会骑马了。