Meaning:

The pinyin acronym of the Chinese term “瑟瑟发抖” (sèsè fādǒu, meaning “shivering”), this secret code kind of usage was invented by and made popular among the generation Z in China. It’s often used by the speaker to express their feelings of misery, fear and frustration, especially when someone is a rookie in a certain field. By showing their weakness, the speaker also tries to arouse sympathy in the listener.

Example:

A: 昨天开会大家都积极提意见，你怎么没说话？

Zuótiān kāihuì dàjiā dōu jījí tí yìjiàn，nǐ zěnme méi shuōhuà？

Everyone else was active giving their opinions at the meeting yesterday. Why didn’t you speak out?

B: 你们都提出了深刻独特的见解，我太肤浅，ssfd。

Nǐmen dōu tíchū le shēnkè dútè de jiànjiě，wǒ tài fūqiǎn，ssfd。

You all gave profound and unique suggestions. I found my thoughts shallow, and felt too intimidated to talk.