'Pì gǔn niào liú' is a vivid, hyperbolic idiom describing extreme terror—so intense that one loses bodily control, literally 'farting, rolling, urinating, and flowing'. Each character contributes to the chaotic physical reaction: 屁 (fart), 滚 (roll or tumble uncontrollably), 尿 (urinate), and 流 (flow or stream). Though graphic, it’s used humorously or figuratively—not literally—and always emphasizes overwhelming, comical panic rather than genuine distress.

This expression is common in spoken Mandarin and informal writing, especially when recounting funny or exaggerated stories of fear. It carries strong colloquial flavor and mild vulgarity, so it’s unsuitable for formal contexts or polite conversation. Native speakers often use it playfully—for instance, describing how a child reacted to a loud firecracker or how a timid person fled at the sight of a harmless lizard.