Meaning:

“起” in this phrase means get up from a bed, and “猛” means abruptly. Literally the phrase means “getting up abruptly,” capturing the blurry state of mind one experiences after bouncing up from the bed. Today’s netizens use this phrase to convey utter disbelief in the face of mind-boggling news. The phrase is often followed by “ 再睡会儿”(zài shuì huì’er), translated as “I’d better catch some more sleep.” It’s like saying, “This is too insane for me to handle right now. I need to retreat into the comfort of slumber and hope it all makes sense when I wake up.”

Example:

A: 快看快看！动物园里这只熊可以站立呢！大家都在怀疑是人扮演的。

Kuàikàn kuàikàn! Dòngwùyuán lǐ zhèzhī xióng kěyǐ zhànlì ne! Dàjiā dōu zài huáiyí shì rén bànyǎn de。

Come and check this out! It’s a bear standing on its hind legs! And everyone speculates that it’s a man dressed in costume.

B: 是啊，太令人震惊了。我的第一反应是起猛了 。看了介绍才知道，原来这是只马来熊。

Shì ā, tài lìngrén zhènjīng le. Wǒ de dìyī fǎnyìng shì qǐměng le。Kànle jièshào cái zhīdào, yuánlái zhèshì zhī mǎláixióng。

Yes, it’s unbelievable. My first reaction was that “I can’t believe they are using a man in costume to play the role of a bear.” Then I learned that it’s actually a Malayan sun bear.