大家在追美剧时肯定都听见过这句话：
Let's put/stick a pin in it.
一、Meaning
那么这句话究竟是什么意思呢？
The phrase “put a pin in it” is an idiom that means to hold on to a thought or idea and return to it at a later time. It is said to have originated in World War II in reference to the pins placed in hand grenades.
“put a pin in it”表示先记住一个想法或观点，过会儿再来讨论。据说这一短语起源于第二次世界大战期间，与手榴弹中的保险栓有关。
In recent years, people tend to use “put a pin in it” figuratively to mean that you should keep a thought in mind so it can be discussed later:
近年来，人们倾向于用“put a pin in it”来比喻应该记住一个想法，以便稍后讨论：
· I think you make a good point, but let’s put a pin in it for now.
我认为你说得很好，但现在先不谈这一点。
· Let’s put a pin in that for now and talk about it when we get home.
让我们暂时搁置这一讨论，回家后再谈。
二、Origin
There is some speculation about the true origins of the phrase “put a pin in it.” However, most people agree that it comes from a WWII expression to do with putting a pin back in a grenade so that it doesn’t explode. This conjures the image of leaving a conversation for later so that it doesn’t explode into an argument.
关于“put a pin in it”这个短语的真正起源有一些猜测。然而，大多数人都认为它来源于二战时期的一个表达。这一表达与把保险栓（pin）放回手榴弹里，以使手榴弹不会爆炸有关。这让人联想到搁置一场对话，以免其爆发成争论。
三、Synonyms
与“put a pin in it”表达相似意思的短语有：
Save that for later；
Hold that thought；
I’ll get back to you on that；
We’ll discuss this later
四、Other "pin" phrases
使用“put a pin in it”时需注意与“pin it on”相区分，后者表示“to blame someone for something, usually a crime”。
“pin”一词本身的释义较多，既可作名词，也可作动词，故有较多相关的短语或习语：
①for two pins
used to say that you would like to do sth, even though you know that it would not be sensible
恨不得；恨不能
【例】
I'd kill him for two pins.
我恨不得杀了他。
②be on pins and needles
to be nervously waiting to find out what is going to happen
如坐针毡，焦虑不安，急得要命
【例】
On hearing the news, she was on pins and needles.
一听到那消息，她就坐立不安。
③pin sb←→down
(1) to make sb unable to move by holding them firmly
按住；使动弹不得
【例】
Two men pinned him down until the police arrived.
两个人按住他直到警察赶来。
(2) to find sb and make them answer a question or tell you sth you need to know
找某人查问；使说清楚
【例】
I need the up-to-date sales figures but I can never pin him down at the office.
我需要最新的销售数字，可就是不能在办公室找到他问清楚。
④pin sth←→ˈdown
to explain or understand sth exactly 确切说明（或理解）
【例】
The cause of the disease is difficult to pin down precisely.
病因目前还难以解释清楚。
⑤pin back one's ears (also pin one's ears back)
to listen carefully
倾听；仔细听
【例】
Pin back your ears, people, this is quite a story!
大伙仔细听，这故事很有意思！
⑥pin your hopes on something/someone
to hope very much that something or someone will help you to achieve what you want
把希望寄托在
【例】
You shouldn't pin all your hopes on getting the job& why don't you apply for some others.
你不应把所有希望寄托在这份工作上，你为什么不申请一些其他的工作？