Meaning:
“反差” means “contrast,” and “萌” means “cute.” First used in ACG (anime, comics and games), the term describes a scenario where a person’s appearance is completely deceitful of their true character, and a comedic effect arises from the huge contradiction. For example, when a hunky man turns out to be very timid and panics over a barking Chihuahua, people may think him “cute” in a funny way. In other cases, this term is used on couples who appear to be the opposite of each other, so that when they show up together, people find the contrast amusing.
Example:
A: 你见过丽丽的男朋友吗？
Nǐ jiàn guò lìli de nánpéngyou ma？
Have you met Li Li’s boyfriend?
B: 见过。像篮球运动员那么高大，但说起话来温柔的像个小女生，特别反差萌。
Jiàn guò。Xiàng lánqiú yùndòngyuán nàme gāodà，dàn shuōqǐhuà lái wēnróu de xiàng ge xiǎonǚshēng，tèbié fǎnchāméng。
Yeah. He’s tall and strong like a basketball player, but the guy talks with the soft voice of a little girl. I think he’s kind of cute with that huge contrast in him.