Meaning:

“白” means “having a light skin complexion,” “瘦” means “slim,” and “幼” means “very young.” This term, reflecting Chinese straight men’s agreed-on standards of beautiful women, has been around for quite some time. Late Taiwanese author Li Ao had proclaimed that his criteria for beautiful women were “tall, light-skinned, slim, young and delicate.” Not a stunning beauty, Chinese actress Yang Mi is thought to be pretty by many men because she is light-skinned, slim and girlish.

Example:

A: 你觉得小李的女朋友漂亮吗？

Nǐ juéde xiǎolǐ de nǚpéngyou piàoliang ma？

Do you think Xiao Li’s girlfriend pretty?

B: 她是典型的白瘦幼，男生会觉得她漂亮吧。

Tā shì diǎnxíng de báishòuyòu，nánshēng huì juéde tā piàoliang ba。

She’s light-skinned, slim and girlish, so I guess men will think she’s pretty.