Correct

马后炮

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Strokes
https://i.cchatty2.com/filters:format(webp)/fit-in/684x0/img/202102/马后炮-Chinese-idioms-Cchatty-69d95767-caaa-4568-8041-f7eabbf8ea53-1612778438.jpg

Collocation

1
马后炮谁都会放
2
放马后炮
3
都是马后炮

Definition

马后炮

Literally means:

fire set behind the horse

Actually means:

belated action or advice

It figuratively refers to belated advice or effort which doesn't help in any way. Derogatory.

喻事情过去以后再提出来的,不能起作用的意见或建议。含贬义。

Example

Used as object or subject. (作宾语、主语)
1
zhèxiē
这些
jiàn
建议
cuò
不错
  
,
可惜
dōu
shì
hòupào
马后炮
le
  
,
yòng
shàng
  

Your suggestions are good, but they're all horse-back guns, and none of them are needed.

2
yǒu
bàn
办法
yīnggāi
应该
zǎo
shuō
  
,
wèishénme
为什么
dào
xiànzài
现在
cái
fànghòupào
放马后炮
  
?

Do you have a way to say, why only put the rear gun now?

3
hòupào
马后炮
rénrén
人人
huì
fàng
  
,
可惜
quándōu
全都
dào
biāo
目标
  

After the horse gun everyone can put, but unfortunately all can not hit the target.