‘吃醋’ (chī cù) literally means 'to eat vinegar', but it is an idiom meaning 'to be jealous'—especially romantic or possessive jealousy. The imagery comes from vinegar’s sharp, sour taste, symbolizing the uncomfortable, bitter feeling of envy when someone fears losing affection or attention to another person. Though the characters individually mean 'eat' and 'vinegar', the phrase functions as a fixed verb expression and is never used literally for consuming vinegar.

This idiom is commonly used in informal spoken and written Chinese, especially when describing interpersonal dynamics in relationships, friendships, or even workplace rivalry. It carries a slightly playful or self-deprecating tone—not harsh or accusatory—and often appears in contexts where jealousy is mild, understandable, or even endearing. It’s rarely used in formal reports or academic writing, but frequent in novels, dramas, social media, and everyday conversation.