Meaning:

“柠檬” means “lemon,” and “精” is short for “妖精,” which refers to a “genie” or “spirit.” In Chinese legends, many plants and animals can turn into a kind of genie if they happen to take a magic pill made by gods or have lived long enough. Therefore, a “柠檬精” is a “lemon turned genie.” This term coined by Chinese netizens refers to those who are especially arrogant and jealous, and like to criticize others who fare better than themselves, ie., an extreme example of sour grapes.

Example:

A: 考试结束我请大家来我家开趴，精心准备了水果饮料零食，小李却嫌我买的东西不够好。

Kǎoshì jiéshù wǒ qǐng dàjiā lái wǒjiā kāi pā，jīngxīn zhǔnbèi le shuǐguǒ yǐnliào língshí，xiǎolǐ què xián wǒ mǎi de dōngxī búgòu hǎo。

I carefully prepared fruits, drinks and snacks for a house party for everyone after the final exams, but Xiaoli criticized me for not buying the best stuff.

B: 因为这次你考了全班第一，所以小李不高兴。

Yīnwéi zhècì nǐ kǎo le quánbān dìyī，suǒyǐ xiǎolǐ bù gāoxìng。

Xiaoli is unhappy because you are top of the class in the final exams.

A: 真没想到他是个柠檬精。

Zhēn méi xiǎngdào tā shì ge níngméngjīng。

I didn’t know he is such a jealous person.