pin down

基本解释

You must pin down every quotation to its author.
你一定要确定每一条引文的作者是谁。
The teacher cannot pin down the essence of ancient poetry.
老师不能清楚地解释古代诗歌的实质。
And for almost as long, some of the world’s best diplomatic and legal minds have retorted that trying to pin down a legal definition of aggression is at best fruitless, at worst harmful.
与此同时，一些世界上最杰出的外交家和律师纷纷反驳，他们认为企图在法律上明确定义侵略罪，不过徒劳无功之举，弄不好还贻害无穷。

"It is very difficult to really pin down and there have been these sorts of accusations from the Revolutionary Guards in the past."
That's a quite difficult argument to pin down does it work or does it not work.
这个论证很难确定,是不是说得通。
耶鲁公开课 - 死亡课程节选
You need to pin down an object of study, a first principle from which other principles can emerge, and part of the process is to say, "Hey, it's not literature we're talking about.
首要原则是，需要锁定要谈论，即学习的目标，可是，谁知道什么是文学。
耶鲁公开课 - 文学理论导论课程节选

Trading in private shares is growing rapidly, though it's hard to pin down exact numbers.
FORBES: Magazine Article

If you try to pin something down, you try to discover exactly what, where, or when it is.
If you pin someone down, you force them to make a decision or to tell you what their decision is, when they have been trying to avoid doing this.