心不酸柠檬酸
[xīn bù suān níng méng suān]
It translates loosely as 'Heart Not Sour, Lemon Sour'. In Chinese online slang, lemons represent jealousy, so the phrase reflects a state of pretending not to care despite actually feeling envious towards others who achieve what we wish for ourselves. It describes being seemingly indifferent on surface when inside truly bothered about comparison to someone else.