To horse around 意思是闹着玩儿，嬉戏玩耍。

例句

During the school holidays there was no peace in the house. Johnny and Annie horsed around all day, every day.

I was horsing around with some friends in the library - we got told to leave.

请注意

短语 from the horse's mouth 意思是指消息来自最直接、最可靠的出处。

Interest rates are definitely going up next month. The finance minister was talking about it on TV - I heard it from the horse's mouth.