Meaning:

Literally translated as “refusing to be defined,” this term was first used by a vlogger on the streaming site Douyin. The young woman posted a selfie-styled video in which she said “Try to be like wind, refusing to be defined.” The short video quickly garnered 2.26 million likes and received more than 80,000 comments. Soon after that everybody was using the term “refusing to be defined,” with some using it simply for comic effect. What people really want to express with this catchphrase is “the freedom of being different and not conforming.”

Example:

A: 我打算去染发。

Wǒ dǎsuàn qù rǎnfà。

I plan to have my hair dyed.

B: 染什么颜色？

Rǎn shénme yánsè？

What color are you thinking of?

A:不被定义的颜色。

Bú bèi dìngyì de yánsè。

Something different, a bit avant-garde perhaps.