声声中国语: 这可不是闹着玩儿的。This is not a joking matter.

这可不是闹着玩儿的。(Zhè kě bú shì nào zhe wánr de.)This is not a joking matter.

Explanation

“闹着玩儿”有开玩笑的意思.这句话的意思是：这不是开玩笑，而是一件严肃的事情，要认真对待，如果很草率地处理这件事，或者没有准备地去做这件事，可能会产生不好的后果。此外，这句话还会用于警告和劝诫某人不要做某些危险或者违法的事情。
“闹着玩儿(nào zhe wánr)” means to make fun of something. While the whole sentence indicates that something is not a joking matter but a serious thing which needs to be treated with attention. If you deal with it casually or without any preparation, the bad consequence will be induced. Besides, it can also be used to warn or persuade someone not to do dangerous or illegal things.
Words:
严肃yánsù:serious;
草率cǎoshuài:casually;
违法wéifǎ:illegal.
Sentences

1、Jiă: Kuài kàn, nàge rén zhèngzài shuǎ dàdāo, wǒ yě xiǎng shìshi.
甲：快看，那个人正在耍大刀，我也想试试。
A: Look, that guy is playing a large broadsword, I want to have a try myself.
Yǐ: Zhè kě búshì nàozhewánr de,nǐ děi xuéguò gōngfu cái xíng.
乙：这可不是闹着玩儿的，你得学过功夫才行。
B: It is not a joking matter. You can’t play it unless you have learned kong fu first.

2、Jiă: Gāngcái pǎobù de shíhou bǎ tuǐ shuāishāng le, xiànzài dòngbuliǎo le.
甲：刚才跑步的时候把腿摔伤了，现在动不了了。
A: I hurt my leg when I was jogging and I cannot move right now.
Yǐ: Gǎnjǐn qù yīyuàn ba, zhè kě búshì nàozhewánr de, yàoshi shāngdào gǔtou jiù máfan le.
乙：赶紧去医院吧，这可不是闹着玩的，要是伤到骨头就麻烦了。
B: You need to go to the hospital immediately. This is not a trifle thing. It will be a big problem if your bone is harmed.